[gauravnawani]

You will need root previlidges for that.

There are few gnome-menu editor around. I havent ever used them but you can try out if you want.

http://www.gnomefiles.org/app.php?soft_id=867
A posting related to that.
http://www.linuxquestions.org/questions/history/338657

I cant recall another editor but it was text based.