As you can’t start the computer because of a possible virus, try the Linux Avira Antivir Rescue system click here
Download it on a working machine, then insert a blank CD-R in the drive, double-click on the filename and follow the prompts to burn it. The file is/was about 50MB in size. On the infected machine, boot from it and when the loading has finished, click on the UK flag, then Start Scanner. Depending upon your computer, the scan will take about 30 minutes.