I installed Vista Enterprise, and a few days later, I received a message:

“Activating Microsoft Windows Vista Volume License Products gives the following error:
Windows Activation Error: A problem occurred when Windows tried to activate. 
Error Code ________________
For possible resolution, click More Information.  Contact your system administrator or technical support department for assistance.
DNS name does not exist.”

After googling the problem I found that if you go to Control Panel > System > Windows activation and click “Change Product Key”, enter the same product key again, and then Vista will activate successfully.