Hi
Please clarify
What is the OS (Operating system) you use ?
Did you made any changes to the system in the recent past?
Please provide the DAT version of McAfee Virus scan (open the Security center -> click on about button -> check the version for all the product)
Try to update the Windows including the optional software update( open IE->click on tools -> Windows update->click on custom)
Try to performed the MVT (McAfee Virtual technician) scan in the system
Link is
http://mvt.mcafee.com/mvt/default.asp and post the session ID in the thread
Regards
Bala