The other answers answer you question, but based on your snapshots, I would bet that your project is configured to use a java runtime/SDK at a hard coded locattion. Try and have a look at your project properties, in the Java Build Path/Libraries/JRE System Library, or in Java Code Compiler. If you see windows-like path, it's not good...
Edit: Sorry, more details:
Open the project properties, by right-clicking its name (Scratch) in the Package Explorer and clicking on Properties (the last entry of the menu I think)
Select Java Build Path on the left, then open the Libraries tab, and develop the JRE System Library item. If you see things like /usr/lib/jvm... you're good. If you see things like c:... that's your problem: the project tells eclipse to look for the java software development kit in a location that is windows-specific.
Hope this help... However, Samik's suggestions seems like a better bet.