To format C means to format the C drive, or the primary partition that Windows or your other operating system is installed on. When you format C, you erase the operating system and other information on the C drive.
Unfortunately, it’s very much not a straightforward process to format C. You can’t format the C drive like you can format another drive in Windows because you’re within Windows when you perform the format. To format C from within Windows would be like lifting a chair in the air while sitting on it – you can’t do it.
The solution is to format C from outside of Windows, meaning you need a way to format a drive from somewhere other than your Windows installation. The easiest way to do this is to boot from an operating system (with formatting abilities) via a CD/DVD/BD drive, flash drive, or floppy drive.
While that all might sound very complicated but it’s actually quite easy to do. Below are several completely free ways to format your C drive, each of which I’ve linked to extensive instructions for:
Note: If you’re trying to format your C drive because you want to replace or reinstall Windows, you do not need to format C ahead of time. Formatting is done automatically during the Windows installation. Skip this article entirely and instead see How To Clean Install Windows.
Important: Formatting your C drive does not permanently erase the data on the drive. If you want to completely erase the information on the C drive, see Option 5 below, Wipe the Drive Clean With Data Destruction Software.
Format C From a Windows Setup Disc or Flash Drive
The easiest way to format C is by completing part of a Windows installation. It’s not easiest as far as number of steps goes, but since most of us have a Windows Setup DVD or flash drive lying around, we have easy access to a means to format drives outside of Windows.
However, it doesn’t at all matter what Windows operating system is on your C drive, including Windows XP. The only requirement is that the setup media needs to be from a newer version of Windows.
How To Format C Using a Windows Setup DVD or Flash Drive
Feel free to borrow a friend’s disc or flash drive if you’d like to try this method. Since you won’t be installing Windows, you don’t need to worry about having a “valid” copy of Windows or a product key.
Format C From a System Repair Disc
If you don’t have access to Windows installation media, but you do still have access to a working copy of Windows 10, Windows 8, or Windows 7, you can create a System Repair Disc or Recovery Drive (depending on your version of Windows) and then boot from that and format C from there.
You can only format C in one of these two ways if you have access to Windows 10, 8, or 7 to create the media. If you don’t, find someone who does and create the repair disc or flash drive from their computer.
How To Format C From a Recovery Drive or System Repair Disc
Note: A Recovery Drive or System Repair Disc can format a C drive that has any Windows operating system on it, including Windows XP or Windows Vista.
Format C From Recovery Console
If you have a Windows XP Setup CD, you can format C from the Recovery Console.
The biggest caveat here is that you must also have Windows XP installed on your C drive. However, if you don’t have access to a newer version of Windows, this option may be your best bet.
How To Format C From Recovery Console
This Recovery Console method to format C also applies to Windows 2000. Recovery Console does not exist in Windows Vista or later, nor does it exist in Windows ME, Windows 98, or earlier.
Format C From a Free Diagnostic & Repair Tool
Several free, bootable, CD/DVD based diagnostic and repair tools exist that have been put together by PC enthusiasts and companies other than Microsoft.
This will be your best option to format C if you don’t have access to any kind of Windows install media and can’t get access to a newer version of Windows to create a repair disc or recovery drive.
Any of these tools that have formatting capabilities will be able to format C without a problem.
Download Ultimate Boot CD (UBCD)
Note: At the moment, the link above goes directly to the Ultimate Boot CD site, one of several programs that allow formatting from a bootable disc. I’ll update this link to a list of such programs soon.
Wipe the Drive Clean With Data Destruction Software
Data destruction software goes a step beyond formatting C. Data destruction software truly destroys the data on a drive, returning it to the essentially the same state it was in after leaving the hard drive factory.
If you’re wanting to format C because you want to make sure everything on your primary drive is permanently erased, you should wipe your hard drive using these instructions.