A GPO is a container for policies that are applied to your domain. Each GPO is assigned a GUID and is stored at %SystemRoot%\Sysvol\Sysvol\DomainDirectory\Policies.
If you delete a GPO, the GUID folder is removed from the Sysvol.
To recover a deleted GPO:
01. Restart you computer and Press F8 to select Directory Services Restore Mode (Windows 2000 domain controllers only).
02. Logon as Administrator, using the Directory Services Restore Mode password.
03. Create a temporary folder on the root of %SystemDrive%.
04. Start /run / ntbackup / OK.
05. Select the Restore tab.
06. Select the proper backup media.
07. Check the System State box.
08. In the Restore Files to box, select Alternate location.
09. Press Browse and select the temporary folder from step 03.
10. Press OK.
11. Press Start Restore.
12. When the restore finishes, restart you server normally.
13. Start /run / dsa.msc / OK.
14. Right-click the appropriate domain name and press Properties.
15. Select the Group Policy tab.
16. Press New to create a new GPO.
17. Rename the new GPO and open its' Properties to write down the GUID.
18. Press OK and Close.
19. Close the Active Directory Users and Computers snap-in.
20. Open the temporary folder (step 03) that contains the restored System State data and navigate to:
21. Locate the GUID of the GPO you want to restore.
22. Delete all the files in %SystemRoot%\Sysvol\Sysvol\DomainDirectory\Policies\GUID from step 17.
23. Copy all the policy files from the old GPO (step 21) to %SystemRoot%\Sysvol\Sysvol\DomainDirectory\Policies\GUID from step 17.
24. Restart your server normally.
See the following Microsoft Knowledge Base articles: