Yeah.. we're going to need computer specs to diagnose problems. SWBF2 does work with Vista.. but can be a pain sometimes. If you do have Vista, try right clicking on the start up icon and selecting "Run as administrator".
SWBF2 sometimes has an issue running with dual core cpu's as well. Check out the "SWBF2 TweakGuide" HERE
for the procedure to turn one off while running the game.
If none of this helps.. post back with your comp specs.