For the meantime choose I have an antivirus program that I'll monitor myself
To do that, in Vista, Go to Control Panel, and in there visit the Security Center. Click on Check Settings next to "Malware protection". Your error message may vary, but click the button labeled Turn On, or an equivalent button in that position. Click on "I have an antivirus program that I'll monitor myself". You should then see "Malware protection" in the security center change from red to yellow, and while it still says "check settings", the state has been changed to "not monitored".