Playing IWD2 on an old IBM XP SP3 Desktop (single core, 1 Ghz, 512 Mb RAM), I've run into serious lag problems on underground levels (Goblin Warrens, Ice Temple, Dragon's Eye). A lot of other threads on this subject suggest tweaking the computer settings, especially on Windows Vista or 7. I couldn't get the game to run on Win7 so gave up and pulled this old XP out of the closet. I tried the major patches and fixes, but to no avail. IWD2 encourages players "to save often." This was causing a lot of problems with load times both at game startup and later on. I was having lag occur inexplicably in the first level of the Ice Temple when I stumbled upon a solution. I created a backup folder in My Documents, then cut and pasted most of my IWD2 savegames into it. I kept only a couple Ice Temple saves plus the Default Save folder. You can find your saves in the mpsave folder where your game is installed on your hard drive. This solution completely cured my lag problems, slow startups and load times. So, thought I'd share it here.