Howto: Configure the Windows 2008 Server Core Screensaver Activation Period

y default the Windows 2008 Server Core screensaver will activate after 600 seconds (10 minutes) of inactivity.

To change the amount of time the screensaver waits to activate, edit the following registry key:

HKEY_CURRENT_USER\Control Panel\Desktop\ScreenSaveTimeOut

I changed mine from 600 seconds (10 minutes) to 1200 seconds (20 minutes).

Sander has several other you can configure for Server Core on his blog.