(reprinted from HowToGeek.com)

We’ve all been at our computer when the Windows Update dialog pops up and tells us to reboot our computer. I’ve become convinced that this dialog has been designed to detect when we are most busy and only prompt us at that moment.

The real problem comes into play when Windows gets tired of reminding us and says that the computer is going to reboot in 5 minutes, and the only way you can prevent the inevitable is to temporarily disable Windows Update.

There’s a couple of ways that we can disable this behavior, however. You’ll still get the prompt, but it won’t force you to shut down.

This trick should work for all versions of Windows as far as we know. You can always resort to the temporary disabling measures instead.

Manual Registry Hack

Open up regedit.exe through the start menu search box or run dialog, and navigate down to the following key, creating new keys if they don’t exist.

HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\WindowsUpdate\AU

Create a new 32-bit DWORD value named NoAutoRebootWithLoggedOnUsers and give it a value of 1 to prevent automatic reboot while users are logged on. Delete the value to put things back to the way they were.

Downloadable Registry Hack

Just download and extract the registry hack files and double-click on WUNoAutoReboot.reg to disable automatic reboots. The other script will remove the hack.

Download WUNoAutoReboot Registry Hack

Using Auto Reboot Remover Utility

If you’d rather not mess with the registry, you can use a small utility created by the guys at Intelliadmin which will make the changes for you. Just make sure you right-click and run as administrator if you are using Vista.