Yes, if you have Windows XP Professional. Log into the account that you wish
to block the command. Next go to Start, Run, and type gpedit.msc to run the
group policy editor. In the User Configuration section expand the
Administrative Templates folder and click the System folder. In the right
pane look for the setting "Don't run specified Windows applications". Double
click it, set it to Enabled, and click the Show button. Now click the Add
button, type in cmd.exe and click ok. You can also use this to block any
other programs you don't want the user to run.
If you have Windows XP Home Edition this will not work since it does not
support group policies. There may be another way to block it, but I don't
know of one myself.