A tough one is that. Sounds like they were EFS encrypted, or had NTFS permissions locking them.
You need to find something that can break that encryption. One of the undersides of security is that sometimes things can get "too" secure.
I installed a new hard drive and reloaded Windows XP. All data files were backed up. After restoring them some, most notably .PST files, were inaccessible because they were protected and the protection cannot be changed even as administrator. They are now sitting on the new hard drive and cannot be touched, not even be deleted. Likewise, some files on an external hard drive (300GB connected through USB port) are protected and inaccessible. How can I remove protection and regain access to my files?