i just built a athlon 2100 with a asus a7v8x mobo, 512 MB of kingston PC3200 ram and a radeon 8500 (i'll upgrade to the radeon 9700 pro if it ever gets cheaper)
I highly recommend going athlon the VIA KT400 chipset , or you can try the nForce chipset but i really dont like that one personaly..
if i were you i'd stear clear of "gigabyte" and "ECS" motherboards, i know so many people who had problems with those, abits are good but in benchmarks they dont compare to the ASUS mobo's with the same chipsets (how very odd..lol)
DONT GET A JANKY POWER SUPPLY OR SALVAGE AN OLD ONE!!!!
i cant stress that enough, so many people i've known over the years try to cut corner with power supplies, computer components are very picky about the amount of power they get and when a janky powersupply can cause your computer to lockup/freeze and eventualy surge and fry everything (i know 5 people this has happened to online and in life not including store bought computers, 9 including store boughts)
thermaltake, antec, enlight and inwin are good IMO