If you have permission, you can grant other user the right to access an EFS encrypted file on Windows XP.
If you are not authorized to add uses to the encrypted file, you will receive:
Error in adding new user(s). Error code 5.
To allow additional users to use the encrypted file:
1. Right-click the encrypted file and press Properties.
2. Press the Advanced button on the General tab.
3. Press Details.
4. Press the Add button.
5. Select a user who has a certificate and press OK.
6. Press OK, OK, and OK when finished.
NOTE: To add the Encrypt/Decrypt command to a right-click context menu, open a CMD.EXE window and type
REG ADD "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Advanced" /V EncryptionContextMenu /T REG_DWORD /F /D 1