Important: You have to have access to a Windows XP Setup CD or a Windows 2000 Setup CD to format C this way. Borrowing a friend's disc is fine since you won't actually be installing Windows.
If you can't get your hands on a Windows XP or 2000 Setup CD, or you don't have one of those operating systems on your C drive, then you won't be able to format C from Recovery Console. See How To Format C for more options.
Follow these steps to format C drive using Recovery Console:
Note: Recovery Console does not install Windows and you will not need a product key to use Recovery Console.
If you don't already know how to start Recovery Console, just click the link above. The process is a little confusing but if you can follow step by step instructions, you'll be fine.
At the prompt, shown here in the instructions linked in Step 1, type the following and then press Enter:
format c: /fs:NTFS
Important: The drive that Windows is stored on, which is usually C, may in fact not be identified as the C drive from Recovery Console. In most cases it will but if you have multiple partitions, it's possible that your primary drive might be identified by a different letter than you're used to seeing. Be sure you're formatting the correct drive!
Note: If you'd like to format C using another file system or you'd like to format it in some other way, you can read more about the format command here: Format Command in Recovery Console.
Type Y and then press Enter when prompted with the following warning:
CAUTION: All data on non-removable disk drive C: will be lost! Proceed with Format (Y/N)?
Take this seriously! You can not change your mind after pressing Enter! Be very certain that you want to format C, which will delete everything on your C drive and prevent your computer from starting until you install a new operating system.
Wait while the format of your C drive completes.
Note: Formatting a drive of any size will take some time; formatting a large drive may take a very long time.
After the format counter reaches 100%, your computer will pause for several seconds.
Once the prompt returns, you can remove the Windows Setup CD and turn off your computer. There is no need to exit the Recovery Console or do anything else.
That's it! You just formatted your C drive.
Important: You remove your entire operating system when you format C. This means that when you restart your computer and attempt to boot from your hard drive, it will not work because there's no longer anything there to load.
What you'll get instead is an "NTLDR is missing" error message, meaning there was no operating system found.
When you format C from the Recovery Console, you don't truly erase any information, all you do is hide it from the next operating system installed. See How To Wipe a Hard Drive if you actually want to destroy the data on the drive, preventing it from ever being recovered.