Did you happen to boot the computer in safe mode and check the status. Tap F8 key while the computer restarts and you will be at the advanced boot option menu.
From the options - Select safe mode with networking and press enter (safe mode with networking could be ignored if you are on a wireless connection)
After all the boot operations, you would be at the desktop, try to update McAfee (if you have it installed) and then run a scan,
Additionally, you could also follow this proposed malware trouble shooting document
Required Reading - Home User Assistance Malware Troubleshooting prepared by our experts , let it find out if its really a virus causing the slow boot up or a system issue.
McAfee Online Community Moderator