Here is a website which scans your computer online without installing any software’s. Just logon to this website and click the button "NanoScan my PC" which will scan your computer within a minute (depending on the characteristics of your PC and the speed of your Internet connection). Once the scan gets over you get the scan result with a summary saying " Your PC doesn't have viruses" (if your PC really don’t have any virus) , time taken for the scan and the name of the ant virus software if in case you have already a ant virus software installed with updates.
http://www.nanoscan.com/