Why do I get an error when I try to reformat my hard disk?

You can't reformat a disk or partition that is currently in use, including the partition that contains Windows. This is a safety feature so that you can't delete Windows by accident. To reformat your computer's hard disk and reinstall Windows, restart your computer using the Windows installation disc (this is commonly known as booting from the installation disc). During the Setup process, you can repartition and reformat your hard disk and then reinstall Windows. The process will erase your files and programs, so be sure to back up your data and program files before you begin. For more information, search Windows Help and Support for "installing and reinstalling Windows."