|That sounds like symptoms of crap installed when you visit a contaminated web site that was placed there by the makers of "rogue" anti-malware software. That crap sometimes makes it appear some of the local drives have disappeared.|
Download and Run Malwarebytes
See response 22 in this
"Malwarebytes will get often get rid of malware that won't allow other anti-malware installation programs, or other anti-malware programs, to run normally."