Many thanks for your reply.
I have submitted all the suspicious files for Comodo to have a look at but how will I know whether they are malware or not? All the files were originally in a folder called "C:\System Volume Information\_restore....." and had names that began with "A00*.* and were either .exe, .dll or.pif files. The only one that wasn't in that folder was "Application.win32.Nircmd.~[at]16774100" which was in C:\Windows
"System Volume Information" refers to the area where Windows keeps its System Restore points. The best way to rid your restore points of malware is to simply delete them and have Windows make new ones.
Turning off System Restore in Windows deletes all restore points (which will delete any malware in it as well). Then you can turn system restore back on after.
How to Turn off or turn on System Restore in XP
Start > right-click My Computer > Properties > in the System Properties dialog box, click the 'System Restore' tab > click to select the 'Turn off System Restore' check box > Click 'OK'. > You should get this message:
"You have chosen to turn off System Restore. If you continue, all existing restore points will be deleted, and you will not be able to track or undo changes to your computer." Click 'Yes' to confirm.
To turn it back on just clear the 'Turn off System Restore' check box.
To turn off SR in Vista, see here: http://www.howtogeek.com/howto/windows-vista/disable-system-restore-in-windows-vista/