Note: It might help to know that a partition usually encompasses an entire physical hard drive. That's why we often say "format a drive" when in reality, you're formatting a partition on the drive... it just so happens that the partition may be the whole size of the drive.
Here are some common things you might do related to formatting:
- Format a Hard Drive in Windows
- Format a Hard Drive From the Command Prompt
- Format the C Drive
- Partition a Hard Drive in Windows
- Completely Erase a Hard Drive
- Wipe a Hard Drive
Important: Formatting the C: drive, or whatever letter happens to identify the partition that Windows is installed on, must be done from outside of Windows. See How To Format C for instructions.
Note: If you're looking for information on formatting an existing hard drive just so you can install Windows on it, don't worry - you don't have to manually format a hard drive to do this. Formatting a hard drive is part of the "clean install" method of installing Windows. See How To Clean Install Windows for more information.
 In Windows XP and prior versions of Windows, the data on a hard drive's partition isn't truly erased during a format, it's simply marked as "available" by the new file system. In other words, it tells the operating system that uses the partition to pretend there's no data, even though there really is. See How To Wipe a Hard Drive for instructions on completely erasing the information on a drive.