Tallima: Sounds like maybe a virus scanner to me. When my virus scanner is going full tilt, that's what it does.
Also, some modern graphics cards can't handle the antiquated 3D graphics in BG 2. If you're playing BG2, you may have to turn off 3D effects. (BG1 doesn't have them, but BG1 using a mod might)
bobtherocket: Playing the first game with no mods save for a widescreen resolution mod. And I don't think it's my scanner, it's never actively scanning when I try to play.
If you've turned off your virus scanner and it's still giving problems, you can look at some of the research I did just for you. :D
I found a good discussion on a similar topic:
http://social.bioware.com/forum/Baldur039s-Gate-1-and-2/All-Baldur039s-Gate-Game-Technical-Support-Self-Help/BG-and-BG2-stutterlag-in-MENUS-and-GAME-5362860-1.html From the discussion:
Do you have a hyerthreaded processor? I've seen a lot of people saying that hyperthreading can cause the problem. Even assigning 1 core won't fix it, though.
If you have an nVidia card, I saw someone say that nHancer sometimes can correct BG stutter. There's supposedly a BG profile out there that will do it, but I can't find it.
Also, someone said (for BG2 -- I don't know if it works for BG) that switching BLT can fix it. When the problems occur, switch it (off if it was on, on if it was off). You'll then get a while of playing, then switch it again when the stutter starts back up.
Also, not installing to Program Files is always smart for old games.
Lastly, from sorcerers.net (again, for BG2
http://www.sorcerers.net/Games/BG2/bg2trouble.php#stutters ) they recommend turning off EAX and turning down ambient sound. I doubt that will help for BG (I don't remember it having EAX, but it might have). But you can give it try if you're up to it.