Quote from here: Install Ubuntu 12.04.3 LTS | Ubuntu
Allocate drive space
Use the checkboxes to choose whether you'd like to Install Ubuntu alongside another operating system, delete your existing operating system and replace it with Ubuntu, or — if you're an advanced user — choose the 'Something else' option.
Question: does choosing the second option "Replace Windows 7 with Ubuntu" delete my drive & drive data also, or does it only delete the C drive?