This also seems like a cool feature or bug.

(This is, btw, a problem we are causing ourselfs because the 
JRE messes around with registry keys when it really shoudn't.
A JRE bundled with a product should remain anonymous and not
be put in the windows registry)

A work-around for Javaws is to always install the bundled
JRE if one does not exist in C:\Program Files\JRE\1.3.0_02 
From the forum:

Hello everyone. My apologies if the question
I'm about to ask has been answered before.

Is there a way to FORCE the JWS installation
program to install its accompanying JVM, vs. checking
the target PC to see if a JVM already exists,
and then using that one instead?

Here's my dilemma. On some PC's at the client
company that I am currently doing work for,
developers have JBuilder 4.0 (I'm using
JBuilder for my example, but it can be any program), which
contains a JVM already. When WebStart is
installed, it does not install the JVM that it came with,
but instead points to the JVM that alredy
exists in a subdirectory of JBuilder.

The problem is then what happens when/if
JBuilder is uninstalled later on? Does the Java apps that
JWS launches all of a sudden stop working,
because the JVM that they are associated with no
longer exists (since it was uninstalled as
part of the JBuilder uninstall (which installed its JVM in the
first place))?

Its a matter of supporting client PC's, and
having to wonder if that in the future the Java business
application will stop working because another
unrelated application was uninstalled. If I could
guarantee that a JVM exists, because I put it
there, then I would feel better about using JWS. I
understand that the user could uninstall the
JVM being installed by JWS, but it is not very likely
that they would do that, while it is more
likely that they would uninstall a program that they
themselves installed previously, that had its
own JVM.

Any advice is appreciated. Thanks for your
time and thoughts.

Adrian Romanelli
Sun Certified Java 2 Programmer

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