1. Start > Run > CMD
2. at 11:20 /interactive “cmd.exe”

You must have the administrator permissions.
Set time 1-2 minutes from now.
At specified time cmd.exe (or any other application) will start with SYSTEM permissions.

To view all tasks
at

To delete all tasks
at /delete

This only works in Windows XP, for Windows Vista and Windows 7 check this article.