9 times out of 10 it's due to either overheating or bad memory. Make sure your CPU fan isn't clogged with dust, then proceed to doing a memory test with MemTest86. The other 10% is due to bad drivers causing conflicts with other drivers. Update your video card drivers and audio card drivers and make sure you've done a Windows Update to get any patches/fixes. Also, if you're using a Creative audio card, be sure you've disabled any onboard sound cards. If you're using USB speakers, also make sure you've disabled onboard sound.
Those will usually correct 99.9% of any issues. Beyond those, it usually requires a reinstall of Windows.