Well it's most consistent with directx games, nothing even that resource heavy, like zsnes, starcraft, and defcon, half-life when I ran it in d3d it didn't happen in open-gl mode. The few other times could've been coincidences, or when stuff actually does start to get too heavy.

My video card drivers have been updated through a few different versions, and direct x has done this with the version that comes with xp and 9.0c or whatever.