Sometimes you need to forcibly uninstall McAfee. Go to the program directory, Common Files and issue: Frminst.exe /forceuninstall Sometimes the forceuninstall fails. And you see all an error having to do with MFEagent.msi. This may be due to a corrupt MSI installer. You'll need to remove references to the MSI by doing thus: Open regedit, HKLM software > classes > Installer> Products > and find the folder that references the "McAfee Agent" and delete that whole folder. Then re-install the agent as normal. In effect, what we're is doing is telling Windows Installer that the McAfee Agent is no longer installed and we're overwriting all McAfee Agent files.