www.resellerratings.com has nothing on them at all. Google reports nothing. I made up a fake name and CC number and submitted an order for XP Professional. It actually told me the CC number wasn't correct, so they have some sort of data validation going on there.
XP Pro for $40 seems too good to be true, so I don't know what to tell ya. I wouldn't risk it simply because all I can find is jackshit info on them, and jack left town.
The products ARE OEM, so they come with no manuals, instructions, boxes, nothing -- only the CD and key. That would be the reason it's so low-priced, but OEM items are usually never this low.
-Lasereth