Windows 7: unable to format local disk C

there it is

It is hard to tell because you did not expand the upper field called "Status". But it looks like your C partition is the System partition which contains the bootmgr.

Please check that. Expand the field "Status" and see whether it says "System" and "Active". If that is the case, deleting the partition would make your system unbootable. Post back and we'll tell you what you need to do.

Please post back a screenshot of your maximized Disk Management drive map and listings:

1. Type Disk Management in Start Search box.
2. Open Disk Mgmt. window and maximize it.
3. Type Snipping Tool in Start Search box.
4. Open Snipping Tool, choose Rectangular Snip, click New, draw a box around full drive map and all listings.
5, Save Snip, attach using paper clip in Reply Box.

Tell us what is on each partition.

Were you not aware you are to boot the Windows 7 installer to install it? If you're installed on D it is because you incorrectly ran the installer from another OS. Do you still have another OS on C?

Greg, there is a screenshot 3 posts ahead. But you can't see much because he did not expand the status field. But since the C partition is the only primary partition (judging by the color), I assume it contains the bootmgr.

Righto Wolfgang - just asking for the fuller DM screenshot to confirm all the flags..

C is clearly System holding the boot files, which is why it won't format and likely had/has an OS he ran Windows 7 installer from.

D has Windows 7 as signified by boot flag but can't host boot files since it's Logical. So he can either convert D to Primary to claim the Windows 7 boot files allowing C to be formatted, or leave the C boot partition as it is having a data partition host the boot files.

I would myself either reinstall Windows 7 to C or if he wants Win8 install it there which itself would take care of the 7 boot files by configuring a Dual Boot.

this is enlarged image .

Your bootmgr and bootmenu are on C!! How did you install Windows 7?? It looks drive letter C was already in use when installing Windows 7. So not done by booting by Windows 7 install DVD. Did you install Windows 7 when booted in another Windows 7/vista/winxp?

As greg told you ... first convert D (your Windows 7 partition) to PRIMARY with partition wizard.
How to set partition as Primary with partition manager?
Post screenshot of disk managment afterwards

BTW why do you want to delete C? Do you want to add that space to D?

When i was using xp it was installed in C but after that i have installed 7 in D and formated XP which was in C .

So you installed Windows 7 from within winxp (which already has C assigned).

Not a real problem. Except the fact that most tutorials point to C drive in explanation. And some bad written scripts reference to C.