First of all, you'll need to create a boot floppy. Here's how you create one:Insert a floppy into the computer's floppy drive.
Format the floppy disk by opening "My Computer" and right-clicking on the floppy disk image, and choosing "Format" from the contextual menu.
In the settings section of the Format window, choose "Create MS-DOS startup disk".
Click "Start".
Now that you've done that, you can boot off the floppy disk that you created. Make sure it's still in the drive, and reboot the computer.
Once you've booted with the floppy, you'll reach the command prompt. There is a Format command on the floppy, but I doubt that will work because usually, Windows XP uses the NTFS filesystem which Format doesn't support. To get around this, you'll need to use Fdisk to delete the partition:Enter FDISK and press return.
In the Fdisk menu, choose "Delete Non-DOS partition". If there's more than 1 partition listed, choose the one that contains the C drive.
Confirm your choice, and delete it.
There's probably no more partitions on your hard drive, which is hopefully what you want, as the DOS tools contained on the diskette can't recreate NTFS partitions, although the Windows XP installation disk is perfectly capabe of doing that.
