Toss that power supply. If your willing to spend $70-$80 bucks go with a Enermax 431W PS & you'll be done.
Motherboards, avoid Abit like the plague. The KG7 is the older model, I ran it along with the KR7. Their easy to kill & their not very stable. Most AMD based Via board don't run for shit with 2 DDR's in them. 1 or 3 is the rule of thumb. The best bet I've found & it's extremely stable is the MSI board. KT3 Ultra ARU. Very nice board.
Hard Drives, IBM well IBM is gone except for the notebook drives, WD wouldn't touch them, Maxtors have detection issues (yes even with their latest models) with newer motherboards. The drive I ended up using is the Seagate Baracudda IV, 20/40/60/80 GB not a single one has died yet, very quiet even under heavy access unlike the IBM's, they do run a little warm so be sure to have airflow across them.
Video Cards, any GeForce card will do (make sure it has a fan on it) or the ATI Radeon's BUT don't even TOUCH a Powered By ATI Radeon, they don't use the same drivers that the Built By ATI cards use & are rarely updated. Plus I had a bunch of stability issues with a Powered By ATI Radeon 8500 128MB, sent it back for another, same problem, sent it back for a Built By ATI & it works excellent. ATI cards tend to look better in games as well.
Ram PC2100 is fine unless you plan to overclock. Go with a major brand, Viking is trash, always here horror stories on that junk, but Corsair, Kingston, are good choices. OCZ is useless unless you plan to overclock. Don't buy the cheap stuff. PC2400, PC2700 just makes your ram usable for future processor upgrades.
CPU, forget the P4, pricy, really doesn't run nice unless you run RDRAM which is pricy. Go with an Athlon XP1800, price/performace it's still the best bang for the buck. If you want a efficent quiet cooling setup go with a Alpha PAL8045, yes you can kill somebody with it but it really does wonders drawing the heat off the CPU even with a slow speed 80mm fan.