DreadPirateMurphy
Explorer
Yep, that. I use BGTutu, but there is also an option to play BG and BG2 straight through. Note that you have to have both games installed, and I recommend a full install for both if you have the disk space.
Runs fine on Vista with a little very minor tweaking. Only problem I've seen is an infrequent crash when leaving Beregost and a strange inability to sell magical crossbow bolts at any of the vendors. Oh, and the journal entries for the prologue appear under Chapter 1. More than worth it, if only for the faster character move speeds in-game and the ability to buy ammo in bulk rather than one lot at a time.