I have just had the same problem. Once you get it to look at the a: drive first, then use the boot floppy. If you still can't use format command then type fdisk and enter. Delete all of the partitions then reboot the computer with the boot floppy. Then using fdisk again, create one dos partition to maximum size and reboot again with boot floppy. You can then carry out a full format c:
This might not be the fastest way, but it worked for me this week!!!