The answer = 0!

A few seconds, well Ok.  But let's say that you cancel because it's taking
so damn long (even with a broadband connection).  Is it reasonable to wait
10 minutes?  Obviously not.  As a software developer, I know that the number
1 criteria is user response.  I also know that more advanced developers
usually allow a thread to be signaled so that it can be timed out, usually
with an event.  So MS is using IE components to download - that's fine.  But
spin off a thread that calls the IE components and that can handle the
cancellation request.

And for those of you who will tell me to use automatic background updates, I
don't want to!  MS provides the capability to update manually, and it should
work properly.

My 2 cents.

RickB