I posted a while back that the classic computer rpg Planescape Torment was available on Good Old Games for ten bucks. Since then they added both Baldurs Gate games, the two installments of Icewind Dale and Bioware’s Neverwinter Nights for ten bucks each.
The games are DRM-free and include the manuals in odf, soundtrack audio files and all the expansions. Gog uses an emulation layer so you should have few technical problems running them in XP, Vista and W7. But don’t quote me on that last bit–check their support forums.