If it is not a overheating issue then it must be virus problem. You can run "Recovery Program" to solve this issue. Usually, recovery program doesn't affact your files, however, for safety, store all your important files on CD or external USB storage device and then run recovery program. To run recovery program, restart your computer and keep pressing "F10" function key (for your computer version) and then just follow the guide to run Recovery Program (it will take couple of hours). Once everything is done, it will once again load the Norton Internet Security (60 days trial version) on your computer (as a part of Recovery). Scan your computer (Full Scan) to make sure computer is safe and working ok. Do not forget to scan files which you saved on external storage device (may be one or more files corrupted with virus). Make your computer virus free and enjoy.....