I'm John Harbeson A+ NET+ Server+ MCSE MCSA, MCDST, MCT small business specialist and some other certs.
I had a system that got a virus and antivir removed some files. rkill, combofix, malwarebytes, atfcleaner did not help; the screen resolution stayed at 640X480.
I just now fixed it by loading the original video driver. Device manager would not load the driver because the version of the installed driver had been modified. I had to run the setup program from the CD.