A lot of applications, updates and drivers force Windows to restart, sometimes without the option to stop that from happening. ShutDownGuard is a free application that helps you “guard” against such unexpected shutdowns or restarts.ShutdownGuard tries to prevents applications to shutdown, reboot or log off your computer. When it prevents a shutdown in Windows XP, it will pop up in the tray and ask you if you want to continue. In Vista and Windows 7, you will see another dialog.
Note that ShutdownGuard will not be able to prevent all shutdowns, since some programs explicitly tells Windows to force the shutdown. This means some programs will still be able to shutdown your computer!