My main rig is an i7-920 box built in '09 and still cruising along. That replaced a 2.4GHz Pentium 4 box which is still sitting in my closet, which is probably the oldest working computer in the apartment, although the Windows XP install on it is borked and I can't remember the Administrator password to restore it. I can still get it running on an Ubuntu LiveCD, but I haven't done that after backing up the hard drive to my external drive when I built the current rig.
My wife's box is an i5-2500K, if I recall correctly, built last year as something of a wedding present, replacing her senile old MacBook from ~2006 or so, which is in a drawer somewhere.
Somewhere in the junk room, though, is an old IBM Omnibook with the built-in pop-out mouse, vintage '97 or so. It might still be able to boot to DOS, although I haven't really messed with it in probably six or seven years now. At this point, if I wanted to get anything onto or off of it, I'd either have to sort out how to access it via ethernet (not sure how to do that through DOS, honestly) or find a machine with a working floppy drive to relay to/from a USB (it has an external floppy drive with an oddball port, but the one on my old desktop hasn't worked since about '03 or '04).