I was going to use my old AMD 400 but a neighbor gave me his old PC so...
Celeron 700
128 Ram (I think)
Onboard video, it's an HP machine.
Runs latest version of MAME but not all games work well, like Galaga 88 lags a lot. But older classics (which were the reason I built the machine in the first place) work great.
Will be upgrading to AMD 1.33 gig 256 RAM when I get around to it.