Give THIS a try:
Do a full install of the game (you mentioned you have plenty of HD space) and run the latest (
http://www.interplay.com/bgate2/patchinfo.html) patch. If this doesn't work, try adding a "no CD" crack to the full install so that the CD isn't involved in the gameplay. The system you listed above should be able to handle the 2D sprites engine, so a compatibility issue with your basic hardware shouldn't be the problem. The other thing I would suggest is that you make sure your video and sound drivers are compatible with your OS (I use XP and it runs fine), and that you check the Microsoft website for the latest, greatest DirectX components. Good luck!