Depends on the OEM, Fujitsu had mine on record when I asked for the XP downgrade, DELL has our work ones tied to the serial # (it shows up with *** in our master lists too when we do the upgrades every 18months as part of our contract with DELL).
Really depends on the OEM, some track them and some don't, Gateway couldn't even tell the OS I had let alone details.
I'm not saying they all do it, but it's pretty much his only option, M$ isn't going to do something from a third party although asking has helped some people in the past during the early launches of XP and Vista where there were alot of issues, but they are the exception, far from the standard IMO.