If the anti-virus has found these in the System Restore backup files, then the easiest way is to disable System Restore then immediately re-enable it. That will delete all those backup files where viruses can hide.

To disable System Restore, find your My Computer icon, right click it and select Properties. In the System Properties window click the System Restore tab, and select the disable System Restore option, click Apply. Then remove that selection and click Apply again. It is always best to re-scan with your anti-virus afterwards.

Mark