Unable to format Drive D:

Hi,

I am unable to format drive D, It shows an error "Windows was unable to complete the format"
even in disk management the format option is not click-able for drive D. I had windows 7 Installed in it, and later I installed windows 8.1 in drive C. right now I am using windows 8.1 and I have also deleted some important system files that were in drive D, so windows 7 is not usable, and I don't want to use it.
Please Help.........

The boot files for Windows 8 are in that partition, thus it is marked as System and Active.

Expanding a little on what Saltgrass said, you can't format a drive that the system was booted from. You would need to boot from an install disk or something like that to be able to format your D: drive. Of course, if you format that drive you would then need to re-install the OS. Is that what you want to do?

You could move the boot files, but you can't move them to a Logical partition. Since part of the drive configuration is hidden in the attachment, hard to tell what is behind the menu dialog, except that it is a primary partition.

Let us know.