If you were downloading some important files you might not want the computer to reboot automatically.The quick way to disable the reboot for the current session is to stop the Windows Update service from running.
You can also suspend the process with Ps Suspend and the command pssuspend wuauclt. Right click on the found program and click Run as administrator.
Enter the command net stop "windows update" and you're good to go.
Open Start menu, right-click on Computer and click Properties.
This will open System dialog box that will show basic information about your computer.
You can do this by opening an administrative mode command prompt.
Type into the start menu search box, and use Ctrl Shift Enter to open in administrative mode.
In other words, this is your one-time off solution.
Run and enter the following command: net stop "automatic updates" OR sc stop wuauserv.
You might also be downloading a large file or letting a lengthy operation run while away from your PC, expecting it to be finished upon return.