Antivirus; there can be only one

Please, do NOT install more than one antivirus application computer at a time. If you install more than one antivirus program that actively scans your computer they will be competing with each other for system resources! It's best to only run ONE at a time. I recently cleaned up a PC that had FIVE antivirus programs running at the same time. Can you imagine what happens when all five of those programs try to scan the same file at the same time? The irony behind it all is that even with five antivirus programs running at once they still had malware on the computer!

My guess is that the conflicting antivirus programs slowed the computer down more than the malware..

If you're in need of good free antivirus, my current favorite is Microsoft Security Essentials.