[Mr Lazy]

I doubt very much you'd need a driver (especially with XP) for what is essentially a removable hard drive using a USB mass storage device interface (when plugged into USB of course). If that was the case I'd expect a yellow question mark to come up against it in Device Manager, but it sounds like it's not seen at the hardware level, so you might be right and it's faulty. You're trying it with just either the USB or eSATA cable plugged in, right, not both at the same time?

Have you looked in Disk Management (under Computer Management) to see if anything is seen there? Can't think of anything else right now. It's a SATA hard disk, right?