My dad upgraded norton antivirus on his computer 2 months ago and during the install something got corrupt and fucked everything on the computer. None of the .exe files would work and you couldn't reset it to another time or date. I let the computer sit for a day turned off brought it downstairs booted it in safe mode, and everything worked just fine. Restarted the computer and everything was fine. That is the only problem I have had with norton in years.