I did this in high school, it was just a basic script that spawned a warning dialog box (the kind thats always on top) that just said you can’t close this, part of the script action was making tge task scheduler check every few seconds if the script was running… If it wasn’t then run it.

Since I was making the task scheduler do the checking it meant even if you tried to task manager force close the script it would just open again in a few seconds, it was not a permanent task it was a temporary one and every opening of the script would reset that task so basically the only way to get rid of it was to restart the computer as that would clear the task.