How to format C disk in windows7

I used XP installed on the C drive, it is FAT32 format and now installed a Windows7 on the E drive. Now I want to put the C drive in Windows C, but I found it after I deleted Windows XP. I can't write it... but now I can't install Windows 7 in C. How can I ask?

There is a Windows 7 installation tool and CD-ROM installation to extract the image to the root directory of the D drive or D drive and then run the Windows 7 installation tool to restart the computer into the installation interface format C drive and then choose to install to the C drive and The CD is installed exactly the same as the tool you can send 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 boot disk in the main disk C disk DE disk, how many logical disks you have now 2 choices First, re-install the system grid C drive to install the C drive system; Second, keep the C drive to maintain the current shape.