hey,
what kind of hard drive is it? (IDE, SATA ...) i know for IDE u just plug it in and its good to go. you can use windows xp disk manager to format it, or any other software like partition magic. theres very little risk of losing your data unless you choose to format the wrong drive. just make sure your computer has an available power connecter and ide cable. also put the second hard drive into slave mode (use the jumpers)
good luck