Assuming you are using Windows. What you do is go to My Computer (on XP, for Vista and Windows 7 it's something like Computer) and right click on it. Then go down to Manage. When that opens up go to Disk Management. There, you can go to the drive you are trying to format and decide how big you want the partition to be and what kind of format you want (NTFS, FAT, etc.). The best thing to do is to look at one of the videos found here on WikiAnswers, that's how I learned how to do it.
This is the video I used:
http://video.answers.com/how-to-format-or-partition-hard-drives-247683034
It means that you are currently using a file or files on the hard drive you are trying to format. If you are trying to format your primary drive you will need to boot to a boot disk - not the C: drive. For most versions of windows you will will need to make the boot disk(s) (an option under My Computer) and boot to those disks rather than your hard drive.
How do you get a computer to boot up with no hard drive? What are the steps or what is the process of getting a hard drive installed into your computer if it is not bootable because of a missing hard drive.
You'd need to boot from some other drive and then use a utility to format the hard drive. One that you can get for free is called DBAN ("Darik's Boot and Nuke"), which will not only format the drive but completely erase everything that's on it. You'd then need to get some other installation media to install a new OS on the hard drive.
No.
Once the hard drive is installed in the computer, you must fdisk then format it the way you want. Next, you should set the bios to boot from the OS installation disk.
you can format your drive from DOS, but once you do that you wont have an operating system and your computer will be useless.
The best way to format your hard drive without a Windows disc is to obtain a copy of Linux (any distribution will do) and run the installer, making sure that you select options to use the whole hard drive. You will then have a hard drive with Linux on it which you can either keep on your computer, or install another OS on top. An alternative method is to use Darik's Boot and Nuke, which will destroy the data on most hard drives. You can get it from dban.sourceforge.net.
For any disk OTHER THAN THE ONE YOU BOOT FROM, simply open a command prompt and type: format d: (where "d" is the designator of the disk that you want to format) OR open windows explorer, select "my computer" then right click on the drive you want to format (again, it can't be the disk you boot from" If you want to format your C drive you'll need to boot from some other medium, such as the installation disk or a floppy.
A CD-ROM drive is not needed to boot the computer. Just put the hard drive first in the boot order in the BIOS.
Yes. In fact the hard drive is the most common boot disk.
If it's not formatted FAT32 already, you will have to format it to FAT32 which erases the data on the drive.
If they are on separate hard drives you can generally just delete/format the hard drive with the OS that you do not wish to keep. If they are on separate partitions on the same hard drive you may have to reinstall the bootloader after deleting/formatting the partition.