Sometimes Windows servers seems take forever to shutdown escpecialyl the one with Active Directory or ISA or Exhange installed on it. I’ve known several people who’ve caused problems for themself by geting impatient and shutting off the server via the power button, rather than waiting for a graceful shutdown.
You can try this one :
-)Start Registry Editor. To do this, click Start, click Run, type regedit in the Open box, and then click OK.
-)Locate and then click the following registry subkey:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control
-)Double click on WaitToKillServiceTimeout
-)In the Value data box, type 120000, and then click OK. (in miliseconds)
-)Quit Registry Editor, and all you need to do is reboot the server
Credit to: http://support.microsoft.com/?kbid=827610
