They do different jobs. You don't need both to wipe your machine.
If you are disposing of your machine(s) by sale or gift to new users, or just reinstalling from scratch, my advice these days is generally not to use DBAN (which has not been supported for several years), but to use the facilities provided with the machines (restore disk(s) and/or restore partition) to return the machines to factory condition, then install Eraser, and use it to wipe free space on the drive(s). On non-system drives (as on your desktop), the best approach is to quick format the drive, then use Eraser to wipe the free space (i.e. the whole drive in that case).That, in my opinion, is the quickest (and, assuming the factory restore works, most reliable) way to end up with a clean but working machine.
If you are trying to retain the Windows XP licences, and simply give away the hardware, you cannot reliably do this, because the licences will be machine specific, and will fail validation on another machine. For a transferable XP licence, you will need an actual Microsoft install disk, and a standard licence that is not in use on another machine. These will become more difficult to find as Microsoft has now stopped selling XP, and I believe that XP licences are cancelled if they are used for an upgrade to e.g. Windows 7.