Mainly retroprogramming. I tinker with making games for pre-Pentium DOS PCs, and even though I do most of the development on my modern PC and DOSBox, having actual hardware to test on is very helpful. I also have some games installed on my 486, but I usually use DOSBox for the really old stuff. My later retro PCs (a Pentium MMX and a P3 system, so not really 'vintage') are used to play Win95/98-era games that don't run well (or at all) on modern PCs.