i recently had to re-install windows7 and instead of formating the hard disc "C" i did a soft install ending up with a copy of Windows.old. my back up disc was renamed to "K" from its orriginal letter "D" I now want to re-format my 2nd Hard disc (as a backup) but windows says " windows was unable to complete the format " Even trying to use administrative tools has no effect.
can anyone suggest how i can accomplish the formatting?

Is your new K drive the 2nd hard disk? Or do you have 3 disks? I think you only have 2 but want to make sure.

Assuming two, I would first power down the computer and disconnect the data cable from the second drive. Then boot into Windows. Does everything work fine! I just want to establish there's nothing on the 2nd drive that is required during boot.

If that checks out, run chkdsk /r on the drive, or from within Windows, My Computer > K drive > Properties > Tools > Error Checking. Check both boxes and follow prompts to exit. When prompted to run checking at next boot, allow it. Note if this is a large drive, it can day many hours, overnight, or even longer to complete. Let it be until done.

Then see if it will format - you might need to do that from Safe Mode.

chkdsk /R is the more thorough option to check for disk errors, it implies /F.
After you run a chkdsk /R open up computer management and try to format the disk. If it still won't format, there are two alternatives to tossing the disk because its busted:

assume Windows can't fix it and try a third party partitioner like Partition Commander or get a Linux Live CD/DVD that has Gparted installed on it and use Gparted to format the disk (no real Linux ingenius required).

last resort, kill the disk with activ@kill disk. A large disk can take forever to kill, It took me 21 hours to kill a 640GB HDD. After that, you may find success in formatting the disk drive.

Also make sure your data cables, IDE or SATA, are not frayed or otherwise damaged. This could cause dataread issues intermittently enough to prevent formatting the disk which requires full working data cables.