at the draft party a couple of years ago, and under a considerable haze, i heard Birdman yell out the following (about 4 or 5 times, i think) - "don't marry yourselves to players!" he went on to reiterate that idea more than once on the boards, and i believe it to be absolutely sage.
What games are you playing?
If you aren't totally into building your own systems and computers as a hobby, I would HIGHLY suggest avoiding to build your own PC unless you are comfortable dealing with driver issues, hardware compatibility issues, and generally weirdness with your PC. If you are interested in getting into building computers and looking at it from a hobby, I would suggest starting smaller and build just a simple desktop PC for internet/word processing and go from there. It will help you become more accustomed with troubleshooting hardware issues and building your working knowledge.
And thats how you get ants!
Agree with H2oBoy.
This isn't 2000. This stuff is nearly idiot proof anymore.
The only compatibility issues that you need to check are your processor to motherboard compatibility as well as your RAM compatibility (dual channel vs. triple channel). Most motherboard companies will publish known compatible RAM modules as well, so it makes it even easier.
Don't be scared. It's rather easy and fun.
Agree with the last two. The motherboard will come with an instruction manual. It might take a while the first time you put everything together but it isn't that difficult.
I was going to add to my post to buy a cpu/mobo combo. Don't have to worry about buying the wrong type of processor for the motherboard. If you're buying everything online it will also tell you what type of RAM to buy in the description of the motherboard. Those 3 things are really all you have to worry about being some certain type to work.
Make sure you buy as much RAM as you can. Spend a little less on a faster processor and buy more RAM instead.
Combo packages are kind of old school and frankly...not very cost efficient. Getting a mobo and a cpu to match is extremely easy as they are typically pin specific anyway.
I highly disagree with buying as much RAM as possible though. Unless he is doing complex video/photo editing he won't need much RAM. If you go dual channel 4gb will be fine. If you go triple channel, 6 gb is plenty.
Remember, more RAM won't make a program faster (like a game), it just allows the computer to do more things at once.