I'm having a problem with my pc. Once turned on, it runs fine, smooth and fast. But after 2-3 hours of being on, my pc will bogg down and run abnormally slow. I run anti-adware and anti-virus software and find nothing. I un-installed all un-necessary programs. Even leave the cover to the chassi off and a small external fan run on it to keep it a cool as possible. Still getting the same reults. I don't know what it could be. Any suggestions? Any help will be greatly appreciated.