Try installing and running Malwarebytes in Safe Mode.

What were the results of SFC?

If necessary run WDO offline from CD or stick, do SFC from Command Line at boot as shown in Troubleshooting Windows 7 Failure to Start . Once it's disinfected, if System Files won't repair or problems persist you may need to do a Repair Install

Another option is to back up your files to get a perfect Clean Reinstall - Factory OEM Windows 7 sticking with the tools and methods which work best with Win7 so it doesn't become grossly corrupted again.