Deal with the spare HD directly. That means, having only that HD present and out of the enclosure and mounted via cables to a spare system or current system. Disconnect any other HD and "solely" deal with the required HD. Once setup, using the XP install CD or this pgm. "KILLDISK" reformat or wipe out the HD. If using the XP CD, boot-up from CD and when prompted do a reformat. If using the KILLDISK pgm. use it and delete all data(wipe out). After such use, continue to partition and/or reset for OS use, use the XP CD to reformat as a secondary step or any other windoze OS. Though you may want to partition first to the use required. Your HD maker should have provided either with thier product via thier support website any s/w to ready the HD for re-use after a fomat, etc., plus any help guide. All HD makers provide such and is free for d/l if you don't have it and/or an updated version. Just be sure you get the same for the same maker HD, you can't cross-use various vendor s/w, they support only thier products.
for Killdisk source use http://www.killdisk.com and follow thier prompts for d/l.