Like most DIY jobs the key to success is in the preparation. At every step along the way consider what needs to be done and how beforehand- don't just plough on without thinking things through. You could end up having to disassemble something that you fitted in haste or something even worse.....
Do your assembly somewhere with sufficient area for you to work on the case while it is lying flat on its side (for a tower). Make sure that everything you are going to need is close by, especially if you have carpets where you are working. Carpets? What have carpets got to do with anything? Well, when you walk about in your rubber soled boots on that nice bit of Axminster in the lounge you generate electricity. You know, the kind of stuff that gives you a bit of a shock when you touch something metal- static electricity. Even a small electrostatic discharge can be death to most computer components, so you must endeavour not to cause any. Ideally, you should wear an earth strap and earth everything in your work area including the PC's case. However- if you don't go wandering about the house but stay put and make sure that you touch your computer's chassis every time you delve into it you should be reasonably safe. Above all, don't remove any of the components from their plastic bags until you need them. The rule is touch the chassis, pick up the bag and remove the contents for fitting (it's OK to let go the chassis if you have to- just touch it again before you touch the motherboard). If you can obtain an earth wrist-strap from somewhere (try a cable specialist at a local computer fair) this is much safer provided you don't forget to keep it on (that's why you should keep everything you need close at hand!).
The first job to tackle concerns just the case, so take off the cover- if it's an ATX it will normally have two removable sides. I usually fit the feet first, because they can sometimes be difficult to fit after the motherboard is in place and a case without feet can gouge great lumps out of mum's sideboard- if you happen to be using that as your work bench. Generally, you insert the plastic foot into a hole in the base and secure it by forcing a little round peg into it from inside the case If the case is an ATX then it probably came with customisation plates for the area that the computer's connectors occupy at the back. Check which plate matches your motherboard- most boards have a standard layout but there are some boards that can claim to be AT/ATX and these can sometimes be a bit odd. Fit the plate using the screws provided, make sure it fits snugly and evenly; there are generally some clips that need to be pushed into place too Have a look to make sure that you will be able to fit the hard drive after the motherboard has been fitted. It usually can, but otherwise put the hard drive into the bottom section of the 3.5" drive cage.
The next job is to sort out the motherboard ready for installation. If it is a Slot 1 motherboard for a Pentium II/III or a Slot A for an Athlon then you may need to fit the retention mechanism for the CPU. Usually, motherboards already have them installed but sometimes they are just a bag of loose bits. The instructions for fitting should be in the motherboard handbook, but normally you need access to both sides of the board so do it now. If the CPU is a slot type then fit the cooling fan to it. There is usually four 'prongs' that fit through the CPU's board and a sliding spring clip for retention.
Now, you have a choice of fitting the processor and memory to the motherboard or to fit the motherboard into the case. If you choose to fit a slot style CPU or memory now, then you should place the motherboard on a firm but compliant surface- a flat piece of cork or rubber is perfect. Well nearly perfect, it ought to be earthed, conductive material too. If there is any risk that pressure could damage the underside of the motherboard then fit it into the case first. I like to fit slot style CPUs at this point because sometimes they need a lot of pressure to get them into their slots. When you push them in there should be a satisfying click to let you know that they've gone all the way in. The little levers at the ends of the memory DIMM socket should automatically close to "grip" the memory module
Before fitting the motherboard into the case, offer it up into the space to make sure you've got the orientation and position right and identify the holes in the case that need to have 'stand-offs' for the motherboard to screw on to. Sometimes it's not obvious because the case will probably have a lot more potential positions than the motherboard so take your time. Motherboards vary considerably; there are several standards of sizes so the holes and positions vary. Normally you need to find six stand-offs and depending on what came with the case you may have a choice of style. I prefer the metal hexagonal type which screw into the sidewall of the case, but there are usually some nylon 'clip-in' ones as well. I've even been forced to use a combination when the case has come with five of each kind. The metal ones result in a firmer job, but check that you are not going to short any of the motherboard's copper tracks to the case if you use them- that would be unusual but there's always a first time so be careful. Screw everything in firmly, but not too tightly because its easy to strip the threads in the thin side panels If it's an ATX then be careful how you offer the board's connectors up on to the custom plate you fitted earlier. Usually there are spring clips between the connectors and the plate to make sure there is a good RF (radio frequency) seal. Failure to fit the clips may mean your PC will cause interference to your neighbours or even your own radio or TV so don't just break them off! Also make sure that the board fits nice and square in the case or you'll have trouble later fitting your PCI cards.
If you've not already done it, then plug in your memory, CPU and fan Fitting a socket type CPU is very easy because of the little lever at the side of the socket. Just lift the lever, drop the CPU into the socket (it will only go in when in the correct orientation) and push the little lever back The cooling fan for the socket is secured in place with a two part spring clip that secures to protrusions on the edge of the socket. Slot type processors often need more force to get them into their sockets than I'm comfortable with, so be very firm- but try not to break anything. If the board starts to bend when you push your CPU into its slot then you will realise the benefit of that large sheet of cork I mentioned earlier.
Now, a special word of warning here about CPU heatsink/ fan assemblies. On slot CPUs, you should fit the fan to the processor before inserting the CPU in its slot. On socket CPUs the heatsink usually requires the use of plastic lugs on the side of the socket to anchor a 'clip'. In either case it is essential that the heat sink is in flat intimate contact with the CPU over the largest possible area. Some heatsinks actually come with a little sachet of special compound to help prevent the possibility of an air gap between the CPU and the heatsink- if you use this then it requires just a 'smear' not the whole amount provided! You must make sure that the heatsink is fitted as tightly and straight as possible. Any airgap- even very tiny- will shorten the life of that expensive CPU, so be especially vigilant over this task
Next step is to set any switches or jumpers on the motherboard to suit your particular processor. Usually, you need to set the main bus clock frequency which will normally be 66MHz, 100 MHz or 133MHz and the clock multiplier. I can't help you here- you must read your motherboard's handbook thoroughly and carefully on this one.
You will also need to consult the handbook to identify all the positions where those mysterious wires that come from the front of the case are to connect to. Normally all the wires that connect from the case to the motherboard should be threaded through and wrapped round a 'ferrite toroid'. That is a black or dark grey ring about 25mm in diameter and 5mm thick. This is also needed to minimise radio and TV interference, so if its not already fitted then look in the bag of screws that came with your case- you may have one in there. The toroid should be fitted as far from the motherboard as possible i.e. as close to the point where the wires go through the front panel as you can get. When you connect in the LEDs (light emitting diodes) that are supposed to light up on the front panel then they must be connected the right way around to work. Usually, the white wire is negative and the coloured wire is positive. Fans must also be wired the right way around; on better quality motherboards they only go on the right way but if you've bought a cheapo then watch out!
When you've got everything connected up and all jumpers and switches set then check them all again. In particular go round everything that is available on the motherboard and make sure that if it should have something connected to it that it has and that connection is the right way round.
At this point go and have a drink of coffee or tea. You are about half way there.
The next item to fit is the graphics card or VGA (Video Graphics Adaptor) to give it its proper name. Some people would fit the drives now, but I like to do a quick check first. You will need to remove the metal strip covering the AGP slot position because that's where the VGA will go (unless of course you've got a PCI VGA). The AGP socket is a dirty brown colour distinct from the other sockets. Plug your VGA card in carefully, keeping it square to the case so that its metal strip aligns nicely with the back of the case. The hole in the end of the strip should align with a tapped hole in the case; put a screw in here to make the VGA card nice and secure. When the time comes to fit them you should adopt the same care and precision for your PCI and ISA cards (if you've got any) Next you can plug in the power cables. If you've an ATX then you can't really go wrong because there is only one plug and it's polarised. However, if you have an AT system then be very careful. There are two identical plugs that have to be fitted and both are polarised but there is usually no indication anywhere as to which is which. They must be fitted so that all the black wires are together, you should end up with a sequence of wires like this: red, red, red, white, black, black, black, black, blue, yellow, red and orange. If the orange gets surrounded by reds then you're in real trouble Now you can test your computer, but first check the 115V/230V setting if there is one. Plug in a monitor, connect up the mains supply and switch on. If you get some writing appear on the screen of the monitor then you have a working computer. It won't be very interesting just yet, but it proves that so far, so good Also check that the CPU fan goes round as it should.
If the machine doesn't 'boot up' and you don't have anything appearing on the screen then switch off and recheck everything. In particular, check that you have inserted the CPU, RAM and VGA card into their sockets properly- all the way in as far as they will go, especially that CPU.
Cables and Connections
When you've got the machine to 'boot up' you can add any remaining plug-ins and cables. There are a lot more of these on an AT and you will have to accommodate the plugs and sockets on the back panel too. Usually, the motherboard kit comes with the COM ports and Printer port socketry mounted on metal strips that fit where your PCI and ISA cards live. Unfortunately, using these may make some of the PCI slots unavailable for use. If this will become a problem then look to see if the rear of the case has 'cut-outs' available for such sockets. If so, you can knock-out the covers from these cut-outs, remove the sockets from their bits of metal and refit them in the cut-out positions. ATX owners will not have such complications.
Always make sure to fit cables the right way round. Most are flat 'ribbon' cables with what are called IDC (Insulation Displacement Connectors) at each end or along their length. These cables have a red stripe down one edge to show "Pin 1"
Look in your motherboard manual to find out which end of the 'headers' on the motherboard correspond to Pin 1. If you've bought a good quality motherboard then the cable plugs and the headers (plug receptacles) will be polarised and can't be fitted wrongly. On the other hand, if you've bought a cheapo then you are going to be much more vulnerable to error. Not only can you get the polarity wrong, but its very easy to offset the connector by one pin position either along its length or its width. Cheap motherboards don't have connector receptacles at all; the headers, as I call them, are just rows of sticking-up pins.
It's also easy to get the connectors the wrong way round on the drives, though most will have Pin 1 clearly marked. The floppy drive may pose you a problem because there will be two connectors on the floppy drive cable that fit, but only one is correct. Assuming that you are using a standard 1.4Meg floppy drive then you want the connector right at the end; the one after the twist in the cable. If there is nothing marked as Pin 1 then there is sometimes a cut-out somewhere to act as a key for the connector, but you may have no key on your connector (if it's a cheapo!) Sometimes the floppy's connector has a pin missing and that should align with the cable connector having no hole in it at the corresponding position. No? Then you shouldn't have bought so cheap- have a closer look for the Pin 1 i.d. Normally, Pin 1 is adjacent to the power connector on most drives, but don't blame me if yours is an exception!
You can usually slide the drives in from the front; floppy and hard drive at the bottom (3.5") and CD ROM (5.25") at the top. Put the hard drive in first. You may not have room to get them in to their cage from inside the case. Sometimes the drive cage(s) are removable, but that doesn't seem a particular advantage so I slide them in from the front
You have to prise out the plastic covers, or poke them out from behind, and then break out the thin metal sheets that bar your way. These should be held only by thin fillets of metal that break when you've bent the plate backwards and forwards a few times.
Before you insert the CD drive and the Hard drive you must set up whether it is to be a master/ single drive or a slave. It really makes little difference, but you must have one master and only one on each of the two IDE interfaces normally provided. The second drive on an IDE must be set as a slave. There is no ID to set. By the way, some magazine articles I've read recently imply that using the Hard Drive's 'Cable Select' (CS) option might be a good idea- it isn't, or at least you need to be careful. If you are using a 'normal' 40-way IDE cable (ATA33) then you must avoid 'Cable Select'. However, if you are using an 80-way cable then both of the drives on it may be set to 'CS'. In this case the motherboard will regard the drive at the far end as 'master' and the drive in the middle as 'slave'. If you've only a single drive on the 80-way cable then it must go at the far end and may be set to 'CS'- the motherboard will see it as 'master'. If you've a single drive on a 40-way cable then it will probably work in the 'middle', but it is much more electrically sound to put that at the end too, but set to 'master'- not 'CS'!
If the rear of the CD-ROM is inaccessible and you have a sound card then plug in the little cable that is going to connect it to your sound card before you screw the drive in position. This is a cable that is normally supplied with the CD-ROM drive, but also frequently with the sound card- so you've probably got two. When you get to connect the other end to your sound card then don't worry about polarity. Nothing is usually marked and the worst that can happen is that you'll get the stereo channels crossed.
If you are fitting a hard drive to an IDE that supports UDMA-66/100 (or ATA-66/100) then you must use the correct cable and use the connectors in the order prescribed in your motherboard handbook You also have to connect power to all these drives that you've added. There should be a couple of bunches of power plugs emanating from the PC Case Power Supply. Just use whatever plugs are going to produce the neatest job- the less it is like a rat's nest the better your PC will be to work on in the future.
You can fit in the remaining PCI and/or ISA cards now if you want, but I tend to leave "extras" like modems until after I've got Windows up and running.