I've upgraded to Vista and noticed a change in this function.
I have a Service (mtguard.exe) which starts a program (mtdirwatch.exe).

As part of the uninstall, I stop the service (mtguard), and terminate
the application (mtdirwatch).

"Detect Active Application" now returns 603 (process not running) for
mtdirwatch.exe.

When I last tested this worked (which was in XP and an earlier version
of setupbuilder).

mtdirwatch.exe shows as active in the task manager list.

It shows as active using "pv.exe mtdirwatch.exe"
(PrcView v 3.6.2.1 command line utility by Igor Nys)

It shows as active using "pslist mtdirwatch"
(pslist v1.28 - Sysinternals PsList)

But it is not detected by setupbuilder.

Regards,
Alan