How can I get rid of Windows Update reboot prompt?
Not sure if it is the same for vista, but worth a try.
On Windows XP, you can modify a group policy setting to change how frequently it re-prompts you. (start -> run type gpedit.msc)
Look under Computer Configuration/Administrative Templates/Windows Components/Windows Update
The setting you want is called Re-Prompt for restart with scheduled installations. The default is 10 minutes.
You can also try modifying the No auto-restart for scheduled Automatic Updates installations setting found in the same location.
Just turn off the Automatic Update service. It will restart the next time you reboot so you'll still get the updates done.
Running this in a command window will stop it until the next reboot.
sc stop wuauserv