THE PRESENCE OF THIS FOLDER IS NOT NECESSARILY DUE TO THE PRESENCE OF A VIRUS!!!
Ok just to clear up a few things, the presence of the 'System Volume Information' folder (on a Windows XP system) in the root directory of each one of your hard drives is completely normal unless you have disabled monitoring of that particular hard drive on the "System Restore" tab of the properties of 'My Computer', if it's still there even after you have disabled monitoring on that drive it is most likely just a remnant that you should be able to safely delete (again as long as monitoring is disabled on that particular drive), note that unless you have indeed disabled monitoring on that particular drive you will not be able to completely delete the 'System Volume Information' folder. The 'System Volume Information' folder is used to store 'System Restore' Data for that particular drive. IT IS NOT AND I REPEAT NOT A VIRUS IN AND OF ITSELF BUT MAY POSSIBLY CONTAIN OTHER FILES THAT HAVE BEEN INFECTED WITH A VIRUS. IF YOUR ANTIVIRUS SOFTWARE HAS FOUND A FILE IN THAT FOLDER THAT CONTAINS A VIRUS THEN THE ONLY SURE WAY TO GET RID OF THAT PARTICULAR FILE IS TO DISABLE MONITORING ON THE AFFECTED DRIVE AND THEN DELETE THE CONTENTS OF THE 'System Volume Information' FOLDER, NOTE THAT DOING SO WILL REMOVE SYSTEM RESTORE DATA SO YOU WILL NOT BE ABLE TO RESTORE THE CONTENTS OF THAT DRIVE TO A PREVIOUS RESTORE POINT.