you can't format the drive that you're running windows from while in windows. use the setup disk to run a recovery console and you should be able to format it from there using format c:
If your Windows operating system is not installed on drive C, you can simply format using the inbuilt formatting tool. Otherwise, you need to boot your computer using an operating system on different drive to format C.
Run the Windows installation and format it from there.
format /s c: should do the job.
format /c followed by the name of the drive you want to format.
Boot from something OTHER than C: The OS will not allow you to format the disk from which the computer has currently loaded. Many OS disks will allow you to reformat the C: drive, and you can even create a bootable floppy that has format capability.
Format drive C
Format the C: drive
If you format a hard drive that contains Windows, it will be removed. Formatting a drive gets rid of all of the information on it. However, you can right-click your C:/ drive and click format, but it will not allow you if your current OS is running on that drive.
If your OS is located at C: drive then you will have to use a bootable floppy or CD. After booting from floppy or CD,you can go to command prompt and them type format C: And if your OS is not located at C then you can do that while running windows xp.
In Windows XP Go to: Start>Programs>Accessories> Command Prompt.At the command prompt enter: format c:/This will format and erase all of the data on the c: drive. If you also have a d: drive then do a format d:/ command before you do the format of the c: drive.Caution: be sure you want all of the data erased as this action is not reversable.
If your OS is installed on that drive yes the OS will be deleted but if your OS is on another hdd then the OS wont be deleted unless you format that other drive. if drive C: has your OS and everything else on it and you format that it will all removed nothing will be left behind. But say you had Drive I: with your OS on it and drive C: with all other data on it and your formatted drive c you would not remove the OS unless you formatted drive I:
It will not affect any other OS providing these other operating systems are not on C Drive.