Best thing for you to try would be a combo of these things:
1) follow the instructions on this page: http://forums.taleworlds.com/index.php/topic,131274.0.html And make sure you have Load Textures On Demand Turned ON. (That setting is in pre-launch menu -> Configure -> Video).
2)
I've made a small resource saving patch that removes all custom D'Shar village scenes and replaces them with native's scenes. This will improve performance a bit.
On my system I used to only be able to load the PoP3301 game with 89% Texture Details when having Load Textures on Demand turned OFF. Now I can load the PoP3301 game with 95% Texture Details (- one notch higher).
Link to small resource patch:
http://www.gamefront.com/files/20182575/ResourcePatch_3301.rar
Be sure to read the included ReadMe.doc that is inside the rar file before you do any installing.
This resource patch is save game compatible.
Regards,
TB