Well... You were lucky and/or patient to find this way.
By the way, has the telephone call cost you anything?
How long have you waited to get XP running on the computer?

And, imagine there was another issue: you get Vista in a language you hardly know, and the seller doesn't have an English version of Windows. Is it possible to downgrade from Vista in Chinese (for instance) to XP in English?

There are restrictions: you can downgrade from "Vista Professional" to XP, but not from "Vista Home".

Googling found it:
http://www.microsoft.com/oem/en/lice...de_rights.aspx

> Only certain OEM versions of Windows Vista include downgrade rights.

> Windows Vista Business and Windows Vista Ultimate include downgrade rights to:
> Windows XP Professional, or
> Windows XP Tablet PC Edition, or
> Windows XP Professional x64 Edition

> Other OEM Windows Vista versions (for instance, Windows Vista Home Basic and Windows Vista Home Premium) do not include downgrade rights.

Could you describe exact steps for downgrade license, please? Maybe, a reader would dig the Vista CD out of thick layer of dust and get this XP license and use non-pirated Windows XP.

But, most likely, if the user hasn't already downgraded, he cannot. He was given "Windows Vista Home", for instance. What a lock!

Anyway, pirating in this case isn't harmful to Windows; it's more stressful to the user who has to fend off the Windows Genuine Advantage.

I repeat: in the case "I pirated it because I didn't want the newer OS" the user has already paid to Microsoft more than he should. You cannot say that the user hasn't paid for the software he uses.