|"McAfee security but it gets an error if I try to run a full virus scan"|
Might we know the error message???
It might be time to just do a clean install anyway.
Be sure to learn and use best practices to avoid problems on the next install.
"Best Practices", Event viewer, host file, perfmon, antivirus, anti-spyware, Live CD's, backups, Make an autorun.inf folder on all usb drives.