Oh, I thought you meant, like, old Windows NT systems ans whatnot. xD This computer is almost 8 years old. We've had to replace the hard drive several times, and I reinstalled Windows once. It was custom built, though, and it has an awesome graphics card in it.
I have a few ThinkPad 760ELs I like to play with from time to time. Built 1997 and I got my first one in 2003. I've used DOS, 3.11, 95, 98SE, 2000 and XP on them (although XP has no graphic card support). I have one 1GB (real 1GB as in 2^30-1 and not in base 10) hard drive and a 4GB SLC SSD for it. I haven't calibrated the batteries for the SSD but it should be rather fun to do so.
It has a nice Pentium I 133 with 104MB of RAM. Yummy.