Shortly after I got my new PC in February, I uninstalled Norton AV 2010 and ZoneAlarm Free and installed MS Security Essentials and let Windows Firewall take over those duties.
Over the next four months I seemed to have no problems. MSSE reported no malware on the many scans and did most everything very quietly in the background. It was an easy program to live with.
Then last week I was unable to get to Desktop. Progress stopped at the Starting Windows screen (black screen with small pulsing MS logo). I could not reach Safe Mode. I could not run Repair Install or Clean Install (both stopped at the Setup window.
I took the PC to a local computer store. After a week they decided I had viruses and cleaned them off.
I guess I should go back to Norton. Over at least ten years I never had an infection while using Norton. Maybe I was getting too adventuresome lately.

Comments would be welcome.