Hi John,
I forget to mention that your scheduled task should be configured for Windows Vista, Windows 7 or above and I apologies for that. Unfortunately Tasks Version 1(XP configured for) doesn't still support user groups. You can configure the task for Vista or above as in the attached screenshot.

- ScheduledTaskGroupSupport.PNG (15.47 KiB) Viewed 12276 times
Also, if you still need to support XP you need to create two separate scheduled tasks conditioning each one based on the installing operating system.
Can you confirm please if this is the case for you?
Thank you,
Nicolae