I've spent two good(bad, actually) days on this already, and searched
through all the archives and anywhere else that the Google might take
me...

I'm simply trying to install the rjb gem using "gem install rjb". I
get this response:
------
Building native extensions.  This could take a while...
ERROR:  Error installing rjb:
	ERROR: Failed to build gem native extension.

c:/ruby/bin/ruby.exe extconf.rb install rjb
checking for jni.h... no
*** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of
necessary libraries and/or headers.  Check the mkmf.log file for more
details.  You may need configuration options.
...
------

I've seen posts about this exact problem, but none of the solutions
work for me (or I'm not executing them correctly, but I've gone
through them all at least 10 times so far).  The proposed solutions
that I've seen are:
1) make sure path environment variable includes JDK root directory.
My path variable includes the JDK root directory, the /bin directory,
and the /include directory (I've tried each individually as well)
2) the JAVA_HOME environment variable not set.  My command "c:\>echo
%JAVA_HOME%" returns "C:\j2sdk1.4.2_17"
3) copy the jni.h (and a few other) files to the rjb-1.1.3/ext folder,
which I have done.
4) run a specific version of the install gem.  I've tried the default
'gem install rjb' as well as 'gem install -platform mswin32' (even
tried 'gem install -platform ruby') and no progress.

Here is some other helpful? info:
OS = WinXP SP2
Ruby = ruby 1.8.6 (2007-09-24 patchlevel 111) [i386-mswin32]
Rails = Rails 2.0.2
Java SDK = J2SE 1.4.2_17
RJB = 1.1.3

Any direction would be greatly appreciated.