This has defenetly nothing to do with Servoy but with JAVA on your machine!
delete every Java under Software
than delete every entry in explorer under c:\Program Files that has something to do with Java
start: regedit and delete every entry that has something to do with Java
HKEY_LOCALMACHINE\SOFTWARE\JAVASOFT.
than restart you computer.
goto:
http://demo.servoy.com:8080
check the link (in the bottom) to check if you have the right JRE installed.
The automated-install process begins and in the end, the java-cup is showing up!
than go back and try to launch the servoy client.!
If that is working, than you can install Servoy Developer.
Good luck!