That worked, however, I can not get it to uninstall quietly.

Altiris refered us to their users guide and the switches they listed were

-s -a /REMOVE /s

So, my script reads now as this, but I tried other variations of putting the switches and I can't get the script to run without a prompt to confirm removal. FYI, the above listed switches does not even run the uninstall.

This is my test script.

$keyname = "{92F2A534-C3E4-4B18-BEBD-329F5E848C8B}"
$uninstall = READVALUE("HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\$keyname","uninstallstring")
SHELL $uninstall + " -s -a /REMOVE /s"