Java 1.7 should have set up files associations on its own, so the easiest solution(for me anyways) is to create a shortcut directly to the JAR file,
"C:\Program Files (x86)\LimeWire\lib\LimeWire.jar"
or
"C:\Program Files\LimeWire\lib\LimeWire.jar"
depending on your windows version.

That should be it, as Java will take over the rest and figure out what it should be doing.

If this works for you, then give me some props, but if not, then suck a dick, 'cus its casual Firday, and I'm drunk, and this works for me.