Plug n Play Manager

I'm trying to track down the source of an Event ID 256 Warning, which is
a message that "an application that registered to receive Plug and Play
device interface notification did not respond within 30 seconds of
receiving a notification event" (see Q262129). Where can I look (file
or registry key) to find a list of the applications that are registered
to receive such notification? The name given in the Event message is
not helpful -- it's "MyTest"