If you have problems with your sound, you should try and reinstall your sound card drivers (but bad sound can also be caused by faulty speakers, ie soundsystems), because thats not usually the reason you would go and reinstall windows. But if the problem's persisting, then reinstalling is perhaps somewhat of a solution.
Reinstalling windows, as I've always presumed, is generally understood as:
1. Copying data from your current system to a medium (CD, HDD, Flash memory, etc) aka "backing up";
2. Wiping your HDD clean (full and merciless formating);
3. Making a fresh installation of windows (& all drivers, of course).