Sound problems on Slash's pc

well the other day my sound went funny then when i reboot there was none at all :<

it appeared that my sound hardware was uninstalled.
-i added new hardware problem solved.

happened again, i repeated the steps , problem solved.

its happened again. 1st with the sound going progressivly more crackly, then stopping altogether. Now when i try add new hardware it keeps saying "problem detected, your new hardware might not be functioning" :@

any ideas ? ive tried system restore too