C-driver properties

[same day]

I'm not a novice user but I have a small problem that is bugging me (making me fell like an idiot really). Everytime I click on c-drive to check the properties, or to make changes, the program locks up and I have to end the process. Even when I am in Windows Explorer or in Admin - storage devices. All of my spyware, antivirus, updates, etc., are up to date and I have restored to a previous date a couple of times to no avail.
What little stupid thing am I overlooking?
Something else that just happened (this I can probably figure out myself shortly, but if you have a clue) my sound when I play a video, sometimes an avi or an mpg, is either non existant or sounds off-beat or slow.
Thanks in advance
Don

Thanks for the advice but I always test my anti-virus & spyware programs with 2 different applications each for confirmation. There is nothing else clogging up the works either. Even with only valid processes running & no programs running it does the same thing. Changed to another user I had setup which has absolutely nothing installed or going on with same result. Ran a program which checks files for corruption and/or changes to no avail. Have all current Windows security updates. There should be a setting in the registry which I can modify to correct this problem but I'm not sure where it is. I am quite familiar with the registry & have used it to correct many problems on my system & many of my customers. Have even ran a program to check validity of DLL files without any luck. Still stumped.