What is your intention? To reinstall? If so, you get that option before you install an OS. If not, grab a Windows 98 boot disk (bootdisk.com) and fdisk/format the drive.
The C volume is only in use when you're on it....therefore you cannot format the root drive from within Windows. That's asking the OS to commit suicide and it won't do it.
As DoubleDwn suggested, the OS install CD will/can format the drive during setup.
Thanks for the support...will do...the problem i dont' have the OS software, will get it tho...yeah just wanna wipe off the harddrive, so i can give my computer away.
If you want free software to completely "wipe" the drive, or zero it out... get the drive's diagnostic software from the hardware vendors site from their support section. Usually they have an ISO that you can create a bootable CD..from there you'll find the options to completely erase the drive so no information is recoverable. (usually known as a low level format, or writing zeros)
Other options...use Google to search for "erasing hard drives".
The program will launch. Go into "Delete partition", and delete any you see. When finished, Go into, "Create Primary Partition", and create one. Once finished, reboot into the floppy again, and this time type in Format C:
It should format the drive.
Keep in mind this will wipe everything on the disk, but I'm assuming that's what you want.
I wrote this from memory, so if anyone sees an error or a way to improve this, just say so. Hope this helps.
