I built my first PC (from scratch) in a PC recycling center when I was working as an intern.
It had an Athlon 64 X2 6400+ (which uses the AM2 socket), 4 GB of DDR2 memory (clocked at 800 mhz), and a shitty geforce 8400 gs.
Funny enough, the CPU has a 125 W TDP, but the motherboard only offically supports 95W CPUs. That resulted in BSODs all the time, so I had to underclock CPU to get a fully stable system.
I actually still have it, because it has a pretty good upgrade path (the mobo has both DDR2 1066 and DDR3 1600 mhz dimm slots and I can plop in a 95W 6-core Phenom II X6 1045T in here).
It´s still chugging along.