This problem is typically caused by internal card readers.
XP assigns drive letters to removable storage first, then hard drives and then CD units.
Before card readers came along the only removable storage you'd have would have been a floppy disk drive and this is why they've traditionally under Microsoft operating systems referred to as Drive A as it was the first drive the operating system would find. In days when it was common to have two floppy drives in a computer (typically 3.5" and 5.25") they'd be drive A and drive B.
Hard drives are assigned next in the priority pecking order, which is why you'll always find on a default setup the CD units come up as Drive D or E depending on how the hard drive has been split up.
Anyway the moral of this history lesson is Windows Setup assigns drive letters to the removable storage devices first (your card reader) from Drive C onwards, then your hard drive(s) and your CD units. This is why it's ended up on Drive H. The only way to get it out of this situation is to basically wipe it again and unplug the card reader before you wipe it otherwise you'll end up in the same situation again.
Edited by Neil Jones, 16 November 2008 - 06:27 AM.