uninstalling

[mohan mohta]

Hello
I just wanted to know how do I uninstall linux from my system I have installed it on my pc in the second partition cause whenever i try to delete the partition from msdos   my first partition it does not allow me to do so.
I wanted to uninstall it completely so that I can install it on the second hard disk which i am going to install in my system .
And i even wanted to ask is it ok if install the second disk of higher capacity than the first disk (forgive me if i sound stupid I am new to the computing world)
thanking in advance
mohan
:-)