There are two resolutions for this problem. You can create a new certificate, or reinstall Zune clean.
Create a new certificate and restore files
1. Create a new certificate
2. Restore third-party files (if you have them)
To restore files, you have to copy files from the .bak folder and paste them into the original folder.
Create a new certificate and restore files
1. Create a new certificate
- If your Zune software is open on your computer, close it, and then disconnect your phone from your computer.
- Open Certificate Manager. To do this, click Start, type certmgr.msc in the Start search bar, and then press your Enter key.
- In the pop-up window, click the Personal folder in the left column, and then the Certificates folder, in the right column.
- Click the heading that says Issued By to sort the column, and then look for one or more certificates that read "zune-tuner://windowsphone/...".
- Right-click each certificate file, click Delete, and then click Yes.
- On the File menu, located in the menu bar of the window, click Exit.
- Click Start and in the search box enter %userprofile%\Application Data\Microsoft\Crypto\RSA, and then press your Enter key.
- Find the folder that begins in "S-1-5-21-".
- Right-click the folder and then click Rename. Rename the folder so that it ends in .bak. This means, you will likely be adding ".bak" to the end of the number.
- As soon as you're done, open your Zune software and connect your phone to your computer. This creates a new certificate and folder.
2. Restore third-party files (if you have them)
To restore files, you have to copy files from the .bak folder and paste them into the original folder.
- Click Start and in the search box enter %userprofile%\Application Data\Microsoft\Crypto\RSA, and then press your Enter key.
- Click the RSA folder.
- Find and open the folder that you renamed to end in .bak.
- Press Ctrl+A on your keyboard to select all the files, and then press Ctrl+C to copy them.
- Press the back button on your screen to return to the RSA folder.
- Locate and open the new folder that begins in "S-1-5-21-" and does not end in .bak.
- Press Ctrl+V to paste the files. When you see the warning "There is already a file with the same name in this location," click Don't Copy.
- Close the folder.