Как отменить команду shutdown / t в Windows?

shutdown /a прервет операцию.

вот список всех аргументов для завершения работы:

Usage: shutdown [/i | /l | /s | /r | /g | /a | /p | /h | /e] [/f]
[/m \computer][/t xxx][/d [p|u:]xx:yy [/c "comment"]]

No args    Display help. This is the same as typing /?.
/?         Display help. This is the same as not typing any options.
/i         Display the graphical user interface (GUI).
           This must be the first option.
/l         Log off. This cannot be used with /m or /d options.
/s         Shutdown the computer.
/r         Shutdown and restart the computer.
/g         Shutdown and restart the computer. After the system is
           rebooted, restart any registered applications.
/a         Abort a system shutdown.
           This can only be used during the time-out period.
/p         Turn off the local computer with no time-out or warning.
           Can be used with /d and /f options.
/h         Hibernate the local computer.
           Can be used with the /f option.
/e         Document the reason for an unexpected shutdown of a computer.
/m \computer Specify the target computer.
/t xxx     Set the time-out period before shutdown to xxx seconds.
           The valid range is 0-315360000 (10 years), with a default of 30.
           If the timeout period is greater than 0, the /f parameter is
           implied.
/c "comment" Comment on the reason for the restart or shutdown.
           Maximum of 512 characters allowed.
/f         Force running applications to close without forewarning users.
           The /f parameter is implied when a value greater than 0 is
           specified for the /t parameter.
/d [p|u:]xx:yy  Provide the reason for the restart or shutdown.
           p indicates that the restart or shutdown is planned.
           u indicates that the reason is user defined.
           If neither p nor u is specified the restart or shutdown is
           unplanned.
           xx is the major reason number (positive integer less than 256).
           yy is the minor reason number (positive integer less than 65536).