Nikon and IBM were pretty specific about that D at the end of the serial number, though I suspect that it's not always at the end of the serial number (note the XHAD in the drive that works versus the XHA in the one that doesn't in one of the posts, above). They will not certify MK1 Microdrives without it will work. That doesn't mean they won't, just that neither IBM nor Nikon would support that combination of products (i.e., they won't "fix" any problems you do have).
Thom Hogan
author, Nikon Field Guide
www.bythom.com
[ August 10, 2001: Message edited by: Thom Hogan ]