Mine is a monster. I pulled the guts for it out of three broken machines, a Dell, a Compaq and an HP.
The processor is a Pentium 4, 2.5GHz x86.
Memory is just 1GB (2 x 512MB). I also have another 512MB stick and a 256MB stick in case these break.
HDD is a very old Western Digital 200GB.
Graphics card: Don't have one. I've got an integrated Intel graphics chipset, 82845G, which has cutting edge technology that supports up to DirectX 6.
I use Windows XP. I use it for work, I use it for home. If there comes a time when I need Vista for work, I'll get it for home as well.
I have named it the FranCompaqraHPenstein, the only thing I pulled out of the Dell was a 512MB memory stick, so it doesn't go in the name. I'm using the Dell mouse and keyboard though.
Before that I had a standard issue eMachine, came with a decent integrated nVidia graphics chipset, 2GB memory, 80GB HDD, and 2.3GHz x86 dual processor. It was stolen along with my TV and stereo. I miss it so much. :'(