Sound Lag

Hi all,

First off I wasn't sure where to post this so sorry if its in the wrong section. Whenever I'm doing something with my media pc the sound will pop and lag. I think its my hard drive but I'm not sure, whenever my hdd led flashes, it pops/lags so I think its my hdd. I can backup my files and format my hdd then reinstall windows as I only have 20GB worth of stuff on there. I've tried defraging my hdd, checking CPU usage (never high), updating all drivers including my sound card drivers, system restore and cleaned out any dust inside the case.

Thanks, Yuilly