Using GPMC in Windows Vista SP1 (and SP2)
Windows Vista SP1 (and presumably the forthcoming SP2) disable GPMC (Group Policy Management Console) after installation.
Fix
Fortunately, this issue can be easily resolved by installing RSAT (Remote Server Administration Tools) for Windows Vista. The package is available the following editions:
After downloading and installing RSAT, navigate to “Programs and Features” then toggle “Turn Windows Features On/Off”.