When you schedule a task using the the Scheduled Tasks GUI, the Schtasks.exe command-line tool, or the AT command, the tasks does not run at the scheduled time. The Scheduled Tasks log contains exit code 80 (ERROR_WAIT_NO_CHILDREN).
To workaround the problem, disable the Human Interface Device Access service:
1. Copy / Paste the following to a HidServ.reg file:
2. Merge the HidServ.reg file with your registry, or run regedit /s HidServ.reg.
3. Shutdown and restart Windows XP.
NOTE: If this does not correct the problem, see Scheduled Tasks do NOT run unless someone is logged onto the console?