I dropped out of the computer geek rat race a few years ago after I built my current system, but jumped back into the loop briefly to build a college pc for my sister-in-law (which was done for $400 not including external peripherals, monitor, or Windows XP, so add another 300-350 for those). It still cracks me up how you state what you want to do and you still get off base and/or over the top answers. So you got a P4? Not to depress you about your recent purchase, but the P4's are old news, and a lot of the newer games are recommending dual core processors.... lucky for me I don't game anymore (I have a 3 yr old instead).
2GB of ram. Find out what kind is in there, and what the maximum ram speed your motherboard will support. If it's regular DDR ram then have fun, you'll spend twice as much on old stuff. If it's DDR2 then you're in luck. Either way, find out what kind is already in there, if it's a single 1gb stick and you can find one speced the same (open the case, look for a sticker on the side of the ram stick. You're looking for brand, speed, and if you're really particular CAS latency) so if you can find one the same get one more stick as a few of the P4 motherboards were capable of running in dual channel mode, which will help you some.
Next check what kind of slots you have to shove a video card into, AGP would be the norm around the P4 era, and is getting a little harder to find, if you're lucky and you get a PCI express slot, then you have a few more options... but be wary because the first generation of PCI express cards were slower than the current 16x and I'm not sure that they're interchangeable.
Oh, and you meant a 160gb HD.... right?
edit: and buy from newegg.com... prices are generally half what you'd find it in a store around here for, and they have a warehouse in NJ so the basic shipping method half the time you get it 24hrs from the time you hit "Place order."
