Notepad is an application that requires user interaction. To run a task when a user isn't logged in, you need to run something that can run unattended without user interaction.
Create a batch file with the following lines in it (make sure the path c:/temp/ exists; it should, but double-check because Windows versions since XP usually don't create it automatically):
- @echo off
- date /t >> c:\temp\task-test.log
- time /t >> c:\temp\task-test.log
- echo ------------>> c:\temp\task-test.log
Then, set up a task that runs that file. You can check the contents of the file "c:\temp\task-test.log" using Windows Notepad to see what times and dates your task successfully ran that batch file.
If this works, then it probably means that the interactive requirements of Notepad are the issue.