Encountering Unsupported major.minor version 51.0

So I have to run Adempiere 361LTS in a Windows 8 machine who runs on Java 7 already.
I've copied my jdk1.6 folder from Windows 7 PC to Win8.

But even though project I've added in eclipse is already being built in Java 6, the eclipse is running Java 7 vm when running the tomcat 6 server. I wanted to debug the system in zkwebui..

So I'm left with logs and result in localhost:8080/webui
UnsupportedClassVersionError... further down the console log of eclipse I read this Unsupported major.minor version 51.0

In this link I read that...

The version number shown describes the version of the JRE the class file is compatible with.

The reported major numbers are:
J2SE 8 = 52,J2SE 7 = 51,J2SE 6.0 = 50,J2SE 5.0 = 49,JDK 1.4 = 48,JDK 1.3 = 47,JDK 1.2 = 46,JDK 1.1 = 45

So this gave me a hint that eclipse though was building the projects in Java 6 it's compiling in Java 7.

Then I found in this link with instructions on how to adjust eclipse version compiler...
Go to Menu-> Window -> Preferences -> Java -> Installed JREs -> Remove the old JRE -> Add new JRE

Finally, I'm able to run the system without error! :D

Hope this helps. :)