I need to disbale ctr+alt+del button on ubuntu 7.1. I modifide /etc/even.d/control-alt-delete to do nothing and rebotted my machine.
When i pressed ctr+alt+del button, I still get prompt to log off.

Plz advise.

Look into the file /etc/inittab
There it is defined what happens when you do this.

On Ubuntu there is no /etc/inittab file. I've made changes in similar file on ubuntu.. but there was no effect. This change works when system boots up in text mode only.

Is it possible for any one to tell me the location from where I can download the source code for for /usr/bin/gnome-keybinding-properties program ?

What file did you change?
After a little research I found that Ubuntu does not use System V init style but "upstart" - and the file seems to be:
/etc/event.d/control-alt-delete
Inside Gnome ctrl-alt-del does do nothing for me too.

Since your second question has nothing to do with the first I suggest to open a new tread on that problem if a google- or forum-search did not yield results. Else your chances on getting this to the attention of people who know are only marginal.
Because I use Gentoo and therefore have all sources and info on them here it was easy to find which package the /usr/bin/gnome-keybinding-properties-program belongs to:
it is in gnome-control-center.

thanks for info

Don't mention it - but actually: there was also a question in there