Building a computer system is not as complex as you might think. The only tools that you will need are screwdrivers. If you have ever added an expansion card to your computer, you are almost half-way to building your own system.

The most complex part is making sure that everything is compatible with everything else that you buy. You need to line up the specs exactly between your parts. For example, if you buy a motherboard with DDR2 RAM memory, you need to make sure your RAM is DDR2.

Once you get all of the required components together you have only to assemble your new computer. You will have purchased a case, motherboard, RAM, hard drive, CD-ROM drives, floppy drive, video card and audio card. Now you have only to assemble them. This usually takes only a few hours and no tools other than the screwdrivers you likely already own. Plus, it is very hard to damage anything. Most cables are keyed so that you are not able to plug them in backwards.

Heaton Research has a complete tutorial, including many photos, of how to build your own computer system.