I've had this problem before... on xp...
I think you'll find that your "Backup DVD," what ever software you used to make the backup... set everything to be "read only" as it was copying to a read only medium.
As others have stated.. you need to undo the read only flag on your files. If your clever then open a DOS prompt and type "ATTRIB /?"
The Attrib command can recursively take the read only flag off all files in a directory. Very nice...
This worked in my situation, have some doubts it might help yours, as I'm not 100% certain of your exact problem.