I have formatted my PC that had windows 7 on it. Before the formatting I have backed up my information.
Now, when I try to access it I encountered a problem:
I have encrypted the files using windows 7 folder encryption and now I have no access to these files. I have the password of the user account.
how do I recover the files?
Unfortunately, I don’t think you can. At least not readily. It might be possible to do (see below) but it doesn’t appear to be terribly promising.
The NTFS “EFS” (encrypted file system) key is stored in the Windows account database (SAM) under lock and key of the user’s login credentials. The EFS key in turn is used in encrypting files for which you select encryption in the file properties.
If it was possible to simply decrypt the files on a different system (which, from Windows’ point of view, is basically what you are trying to do) then that would imply that EFS is ineffective.
If you have a copy of the SAM database (even a copy of a backup should do fine), you might be able to restore that and gain access to the files that way. If so, I suggest you ask how to restore the SAM database from a backup copy. Basically, this will only be the case if you copied essentially everything, including the Windows directory, to your backup media. The problem, of course, is that if the backup itself is EFS encrypted under a key stored in the old SAM database, then you won’t have access to the SAM database copy before restoring that one, creating a chicken and egg problem.
Encryption is easy. Key management is hard.