completely freezes every few minutes

I have a Compaq Presario CQ56. It freezes every few minutes so I am unable to run any diagnostics. I have McAfee and no viruses mal ware or anything found. I think it might be the registry but I can't run the cleaner without it freezing. Anytime I attempted to go into the manager for start up programs (msconfig.exe) or anything like that it freezes immediately and doesn't wait the few minutes.

Windows 7 Home Premium 64-bit Service Pack 1