How to prevent a user from running Task Scheduler in Windows

Prevent users from adding new tasks or deleting tasks in Task Scheduler by modifying local policy settings

Note The following procedure only applies to Windows XP Professional, Windows Server 2000, or Windows Server 2003. To do this in Windows XP Home edition, see the "Prevent users from adding new tasks or deleting tasks in Task Scheduler by modifying registry settings" section of this article.

1. Log on as Administrator to the computer where you want to modify the Local Policy settings.
2. Click Start, and then click Run.
3. In the Open box, type gpedit.msc , and then click OK.
4. In the left pane of the console, expand the Computer configuration node.
5. Expand Administrative Templates, and then expand Windows Components.
6. Click Task Scheduler.
7. In the Task Scheduler pane, do the following:
   1. Double-click Prevent Task Run or End.
   2. Click Enabled, and then click OK.
   3. Double-click Prohibit New task Creation.
   4. Click Enabled, and then click OK.
   5. Double-click Prohibit Task deletion.
   6. Click Enabled, and then click OK.
   7. Double-click Prohibit Drag-and-Drop.
   8. Click Enabled, and then click OK.
8. On the File menu of the Group Policy snap-in, click Exit.

Full detail can be seen at  microsoft help