Heh...
Building a computer is pretty easy once you know what you're doing, but it's not THAT easy!!
Short version....
1. Decide what you want to do with the computer.
2. Find a chipset and Mobo that meet these needs.
3. Pick a processor (usually Intel or AMD, they are NOT compatible with each other. Consider that when picking a board.)
4. Pick RAM (type and size is decided by board, but it's pretty straight forward.)
5. PSU - I would recommend about 500 watt. Leaves room for future upgrades. DON'T GO CHEAP ON THIS PART!
6. Graphics card - depends on budget, gaming, design work, and such.
7. Hard Drive - Newer systems use SATA, older use a ribbin (the really thick one). There is SATA1 and SATA2. SATA2 is a lot faster, but they are compatible with each other.
8. Case - Find a nice quite one with good fans that will fit everything.
I think that's about it, besides from Keyboard, mouse, monitor, speakers, and such. What really depends on what you want to do with it. Decide that, and then we go from there!