My family's first computer was a Commodore PET - one of the first 1,000 made. This is the first computer you didn't have to build yourself and I think my dad got it in December 1977 or 1978 (the box is in their attic and the USPS shipping label is on there somewhere).
The cool thing about it is that it's been in the museum on the bottom floor of the Texas State University Library a couple of times for a computing history exhibit. It's the first personal computer used on the university campus - my dad used to take it back and forth between home and the university every now and then.
Think I win the oldest non-homebuilt PC contest!
