I was actually thinking about finding a second-hand copy of XP and re-building an old computer I have lying around, installing XP on it and use it for older games. Sure, it would only be able to support up to 3.5GB RAM, but if it's only for a few older games I have lying around, so what?

I also might use it for game development with older software (DarkBASIC Classic anyone?), but I almost doubt it. Maybe just for 3D modeling/animation.
I'm running Windows 7 64-bit on my laptop, and I've had a few occasional bugs. My taksbar likes to flicker a LOT for some reason, though I suspect this is because of the Intel Accelerated Graphics Chip. I should look into updating the driver, maybe that'd fix it.
I've also had trouble getting DBPro to work on it, at least with the default IDE (Synergy?), and every time I install a plugin I have to remember to start DBPro "as administrator", or else it crashes and locks up my laptop. That annoys the pancakes out of me. Other than that, I can't really think of bugs I've encountered, it's usually software-specific (like with DBPro).