My computer started out as a 433mhz emachine. It ran Windows 98se, 32mb ram, 4.3 gb hard drive, integrated 4mb video card, and pci winmodem. Since I bought it I made a few changes.
Added: Mandrake Linux 9.0, hard drive controller card, 2-256mb sticks of ram, cd burner, 2-30 gig hard drives, geforce2 video card, and a nic.
I didnt quite build the whole machine, although I could easily do that.