The PC-I (or PC-1) was Commodore's first foray into the IBM compatible PC market, and unfortunately wasn't as successful as they'd have liked it to be! In true Jack Tramiel (or Ken Olsen of DEC fame) fashion CBM decided that what you got was all that you'd ever need, so expandability wasn't built into the PC-I. True, it's a nice compact machine, but once you outgrew it......um....