Massive Lag when fighting Firkraag Dragon

[Outer Heaven]

Currently experience horrendous lag when fighting the red dragon. Ive done the following to attempt to fix it..

 

Turned off hardware acceleration

Set my dual core affinity to 1 core

Installed Application Compatibility Toolkit, found here

 

Still, no dice.

 

Additional info:

 

Im running on

Windows 7 64 with a GTX 460 1gb and 4 gigs of ram. Baldurs Gate 2 SoA/ToB are installed to C/Games, not program files. Im running the game from an .ISO of ToB, with tweak and fix packs from this site, along with widescreen mode, high quality music, and a few other smaller mods.