You will need to close your web browser for this to work. Since you have Stuffit Expander already installed, I want you to open it and go to the Edit menu and come down to Preferences, when the window comes up scroll down to the bottom and click Internet. You will see a button that says "Use Stuffit Expander for all available types" Click the button and click OK. Now I want you to drag the LimeWireMac.bin file to the box that says "Drag your files here" If you don't see one, go to the Window menu and come down to Drag Window. I hope this helps.