HI,
I think this is not possible because Altiris client fetch report after install install altiris client.
You can find manually Altiris Client Not installed system.
Altiris management Console ->Manage ->All Computers ->
Check Where is Managed Symble not showing it's system not reporting Altiris Client.
Or
You may Export all System Report in AD and Compaire With Altiris Client install system