If your onboard sound does everything your sound card does, then switch.
If you require more features than onboard sound has, then get an updated card (check craigslist, ebay, etc...).
Either way, remove the sound card (and driver), then see if you keep getting BSOD.
You might also check to make sure your RAM isn't causing the problem.
Next time you see BSOD, take note of the error and let us know so we can pinpoint the problem.