You can lose access to encrypted files if you install a new operating system or upgrade your current one, or if your current operating system fails. The following steps can help you regain access to encrypted files.
You must have a backup copy of your encryption key and related certificate on a disc or other removable media (such as a USB flash drive) to follow the steps below. For more information, see Back up Encrypting File System (EFS) certificate.
These steps can't be completed on Windows 7 Starter, Windows 7 Home Basic, and Windows 7 Home Premium.
Do one of the following:
To recover encrypted files stored on an external hard disk, connect the hard disk to the new computer.
If your operating system fails and you need to recover encrypted files that are stored on a different partition from your failed operating system, move the encrypted files to a computer that is working, or install a functional operating system on the current computer.
Insert the removable media that your certificate and key are saved on.
Open Certificate Manager by clicking the Start button , typing certmgr.msc into the search box, and then pressing Enter.
If you're prompted for an administrator password or confirmation, type the password or provide confirmation.
In the left pane, click Personal.
Click the Action menu, point to All Tasks, and then click Import. This opens the Certificate Import wizard.
Type the location of the file that contains the certificate, or click Browse and navigate to the file's location, click Open, and then click Next.
If you have navigated to the right location but don't see the certificate you are importing, then, in the list next to the File name box, click Personal Information Exchange.
Type the password, select the Mark this key as exportable check box, and then click Next.
Do not enable strong private key protection.
Click Place all certificates in the following store, confirm that the Personal store is indicated, click Next, and then click Finish.
After you import the certificate, you should have access to the encrypted files.