first for customize your kde menu you
can right click on the kmenu button (usually bottom left corner) an choose menu editor.
It launch the menudrake tools.

Next installing LimeWire in the root directory is
not a good idea expect if you always use the root account (very bad idea).
In my way I launch the LimeWire installation programma as root user in normal user session and I change the default installation directory to /opt.
After installation I create two directory Incomplete and Shared on my user directory
(/home/user/...) next I make a new entry in my kde menu to /opt/LimeWire/LimeWire.

Some advice: always limit the use of root access this why normal user can access to root directory even in read access and than konqueror ask you to give your root password.