Sorry, I can't really help you with the stuttering problem that you're experiencing with BG1. I haven't played that game since last year, and I never had any problems with it other than the occaisonal crash or game freeze. You could try asking some people at the Ironworks. There's still some nice folks who are playing BG1 over there.
http://www.ironworksforum.com/ubb/cgi-bin/ultimatebb.cgi
I'm sure you've already done this by now, but you should try reinstalling the game to see if it helps at all. But if nothing works, then you might as well play some BG2... or maybe go back to classic Diablo
