Hi,
When it comes up to A:, all you need to do is type Fdisk and it will do what you want. Typing Fdisk will take it to the C: drive to do the work for you. When you go there, you can delete the partition, create the partition, activate the partition and then after shutdown, format the partition.
However, if you really want to clean this drive and get rid of everything (Fdisk and format only masks, and deletes some things and does not delete everything), I suggest you use Dban located
HERE. That will clean that drive to like new capacity. You can do that from a boot floppy and the site tells you how to do it. It does take longer, but does a much better job than Fdisk. When you are done, you can use the XP disk to install. This program as I mentioned will take more time since it cleans everything, but most techs on here use and recommend it.
Addendum: Darn, almost forgot. You know that the drive manufacturer's utility will also do a great job with what you want to do. You can download those from this site:
Manufacturer’s websites for the utilities of all drive makes and models
http://tacktech.com/display.cfm?ttid=287