disable clock in xp home

I know I have done it before that there is a registry change that you can do or add to the registry to make it so that when you double click the clock in xp home it will do nothing.
I have searched high and low through out the internet and cannot find it the thing is that I do not want to buy software to do it for me when I know I can do it on the registry for free.

I should also let it be know that I want the clock to stay there

now my question is what is it?