I would guess that you by accident have set the Windows Picture and Fax viewer as default for opening .exe files.

Should be fixable be right-clicking on the Limewire .exe file and choosing (hmm I don't really know what's being used to run .exe files)

(edit: Scratch that. I just tried it and the option to open with isn't there, only "run as" instead. Don't know then. Sorry)