while installing my windows 7

You can manually prepare your hard drive:

BIG NOTE: This formats your whole hard drive, don't do this if you haven't backed up your data!

Boot the Windows Installer.

at the first installer screen press shift + F10 to take you to command prompt where you can run diskpart commands

type: diskpart - press ente (to enter diskpart)

type: list disk - press enter (list all connected HDDs)

type: select disk 0 - press enter (assuming disk 0 is the desired disk)

type: clean all - press enter (which will erase entire disk including partitions)

type: create partition primary - press enter (which will make one new primary partition the size of the disk)

type: format fs=ntfs - press enter (which will format the partition with ntfs structure)

type: active - press enter (to mark partition active so boot files can be placed on it)

type: exit - press enter (exit diskpart)

type exit - press enter (exit command prompt)

Continue the Installation.