You can do one thing. First of all you must have a latest antivirus setup program with you which you can install. It must be either on CD or must be saved somewhere in your system.
Then as you start your system, start pressing F8. Start your computer in Safe Mode as you have been told earlier. Then, scan your system with the antivirus you have. If it does not find anything. Uninstall it and install the antivirus from CD or from your system. Then scan. If it does not find anything. Again restart your system and start pressing F8. Select Option Disable Automatic Restart on System Failure. Open internet explorer and go to this link

http://onecare.live.com/site/en-au/d....htm?mkt=en-au

Click on full service scan. It may take more than 5 hours to complete

I am sure this will solve your problem and your system will be faster than ever.