I'm assuming that this is a malware detection. More details of your operating system and service pack and what McAfee product/version you are using would help.
Try disabling System Restore temporarily, reboot into safe mode (tap F8 repeatedly while booting up), then go to Computer (My Computer in XP) and right-click the hard drive and select scan. All you'll see is activity in the taskbar by the clock.
See if that cures it. Let the scan run its course it will take a while. Hover over the taskbar icon for a progress report.