Who would build a NEW XP machine?
Can you even find a copy for sale?
I like most would have to by a superior OS and use the "Downgrade Rights" as permitted by MS.
IE you may use a Win7 Pro license to install XP, which is legal and probably the only way to get one.
So,... no surprise that the sales are plummeting since new media is not being created. One must by a superior OS to get a license so the sale shows as that of a new OS even though XP is being installed and used.
edit.....
Upon further review I see these are based on visits to member websites.
So it does seem that there is a large drop in XP machines on polled websites.
Perhaps people with XP have been reading your thread .