Boot from cold, and press F8 on boot up. When the menu appears, select start in safe mode.
Once on the desktop, select device manager and see if it is showing any conflicts (yellow exclamation marks).
If so, try re-installing the drivers in safe mode, and then attempt a re-boot normally.
Sound cards (like modems) can be difficult to install, so you could try a different slot, if the above does not help.