I recently installed XAMPP and all was working fine from the Control Panel but then I had a need to run Tomcat...
Ran the Catalina_start script and got the 'JDK Reg Key...' error message.
I was surprised because I had read a lot about XAMPP only needing the JRE now. I only had the JRE installed.
Looking at both the Catalina_start and Catalina_stop scripts they both seem to rely on the JDK being installed.
Anyway I have downloaded and installed the JDK now and Tomcat works fine.
I just thought I would post this so you know about this slight inconsistency.
It will be nice when Tomcat is fully included in the Control Panel, good luck with this.