With the way Windows protects the System Restore files, you can't really delete just one, so you're forced to purge all of the entries. Do do this, right-click My Computer, select properties, select the Performance tab, click File System, select the troubleshooting tab, place a check next to Disable System restore, and OK your way out. Wait a few second then go back and uncheck the box in order to reenable System Restore. All previously created recovery points will have been deleted (it's done automatically when you disable the feature), including the infected one(s).
Hope this helps,
My computer runs on Windows ME. When I run McAfee VirusScan, I get one infected file within an old System Restore point, a file that can't be deleted easily. How can I access the System Restore files to delete old ones?