When shutting down your NT box, the Service Control Manager uses the value set in a registry key to determine the...
number of milliseconds to wait to see if a service has shut down. You can modify this value to speed up the shutdown time of NT. Note that you DO need to provide enough time for the services to shut down, so setting the value to 1 will be of no use. A value of 15000 or greater is probably acceptable.
Note: Registry editing can be risky, so be sure you have a verified backup before you begin.
Open regedit, and go to the following key.