I don't know about you guys, but I would disable it. It looks like a Windows Security Centre alert.
Go to control panel and "Security Center" icon (or double click on that bubble in the picture), then under "Virus Protection", click "Recommendations", then tick the check box that says "I have an Antivirus program that I'll monitor myself". Only do this if you know for sure that your virus scanner is working AND up-to-date!
20/12/2007
Mario and Sonic at the Olympic Games
Gold Coast, Queensland, Australia