But I don't think you want to use TSSHUTDN.EXE on an XP box.
Try PSSHUTDOWN from Sysinternals:
http://www.sysinternals.com/ntw2k/freeware/pstools.shtml
You can use PsShutdown to initiate a shutdown of the local or a remote computer, logoff auser, lock a system, or to abort an imminent shutdown.
usage: psshutdown [-u username [-p password]] [[-s | -r | -k [-t nn][-m "message"][-f]] -a | -l | -o] [\\computer]
-? Displays the supported options.
-a Aborts a shutdown (only possible while a countdown is in progress)
-f Forces all running applications to exit during the shutdown instead of giving them a chance to gracefully save their data
-k Poweroff the computer (reboot if poweroff is not supported)
-l Lock the computer
-m This option lets you specify a message to display to logged-on users when a shutdown countdown commences
-o Logoff the console user
-r Reboot after shutdown
-s Shutdown without poweroff
-t Specifies the countdown in seconds until the shutdown (default: 20 seconds)
-u Specifies optional user name for login to remote computer
-p Specifies optional password for user name. If you omit this you will be prompted to enter a hidden password.
\\computer Shutdown the computer specified