If you need to whip your Cdrive, you are best advised to re-install windows and reformat the drive during the process.
If you have transplanted a C drive from another computer and need to format it, first you need to delete all files, because windows will see system files on the drive and refuse to format it otherwise. Then you can format it normally.
But I need to state again, the C drive on your system is where your operating system is. You really, really don't want to delete it.
you can format the hard drive by booting with your windows disk...in advanced options you will see a list of detected hard drives..you select the drive and on the bottom of the list you have an option to format the drive...its used when you want to re install the operating system