For earlier Windows games that are not 3D accelerated, check out Virtual PC 2007, which is now free. I was surprised by how well it runs a lot of stuff from that period. The best part is that I can use the Yamaha SYXG50 midi driver in it, which makes a lot of midi music I have from older games sound really good. I had gotten this thing on an old ASUS motherboard CD, but the version included there was only for Win9x/NT and I couldn't use it on XP.
I have kept an old PC around for DOS and early Windows games (1.4ghz Athlon, 512MB, GF3+two Voodoo2s, SBLive with SB16 emulator), but I've been using it increasingly less over the years. I originally set it up for the Glide version of Descent 2, but there is a much better modern port of that available now, and Dosbox has gotten much faster with the newer versions, fast enough to run everything I've tried perfectly smoothly. There were still a handful of early Windows games that I needed that machine for, but those work great in Virtual PC and I doubt I'll have much use for that old system at all now. Maybe for Nuclear Strike in Glide mode, although that game runs fine in software and doesn't look much worse.