Should I uninstall Tomcat 6.0 and install a earlier version or is there any other way to make this work?
No, you can leave it. Look into your PATH. Type "SET" at the command prompt, and make sure there's is no directory which has an old "javac.exe" in it. I suspect there's a directory in your PATH containing a different version of javac. For example, if you have installed Oracle in your machine, it might add its own directory in the PATH, which contains a java compiler.