This is not a Limewire problem, it is a user access issue in OSX.

Control click your hard disk, select show info and choose Privileges in the popup menu. Make sure access is set to read and write.

If this option is greyed out, then you're not signed in as administrator.

Go to System Preferences>Users and this will give you a list of users available on the computer. There should be one labeled Admin.

Go to the Apple menu and select Log Out and Log back In using the ID of the Admin user. If you don't know the password, ask whoever set up the system to do it for you and change the access privileges on the hard disk as I described so you can install LW.