Windows7 how to format the C drive?

I originally used XP installed in the C drive, is FAT32 format and now installed a Windows7 system in the E drive now I want to put the C drive I installed Windows 7 in C, but I found it out after I deleted Windows XP... but now I can't install Windows 7 in C. How do I get it?
There is a Windows 7 installation tool and CD installation. Unzip the image to the root directory of the D drive or D drive and run the Windows 7 installation tool to restart the computer. Enter the installation interface and format the C drive. Then select the installation to the C drive and the CD to install exactly the same. You can send the tool to you.
There is also that you do not re-install the system to go to the C disk, you can not enter Windows 7 boot file, the number of the logical disk in the main disk C disk DE disk, you now choose 2, one again Install the system grid C drive to install the system C drive; Second, keep the C drive to maintain the current xp system download.