Not the baddest piece of machinery on earth, but a friend unloaded a Pavilion 505w on me;

2.4GHz Celeron

512MBs of RAM (2GB system max)

80GB Seagate

DVD-ROM/CD-RW combo drive

An ASUS mATX board that's lacks AGP, but has 3x PCI available.

I may throw some more RAM in there or use the fact that I have a nice case and optical drive as a reason to buy a 780G-based mATX board, some DDR2 and a 45w Athlon 4850e.