All you have to do is buy a new copy of Windows XP. Stick the disc in the drive. Windows will begin installing itself.As the hard drive has no operating system on it, chose the option to format the drive and install a new copy of Windows. As for where to get XP, NewEgg.com (Very reputable PC parts website. I've been buying from them for years) still has Windows XP in stock:
http://www.newegg.com/Product/Produc...82E16832116056