Umm.. a friend of mine got a laptop just last week. That and an other machine were the only ones out of 15 sold models that had Vista on them. That was one of the leading mass-retailer chains...
We've got 2007 now and MS will only stop supporting Win2x from July onwards. That's quite some time. If the marketing concept of Microsoft was an economic one, they'd stop supporting Win2x right after the release of XP, thus forcing an upgrade as well.
However, they've got an image to keep up to and shall they stop supporting XP's multimedia capabilities to simply receive a gross cashflow in the next couple of month, the trademark's image restoration costs, that being that of Windows and all other products of MS, would be far larger than they could win with a single product. Their focus is OEM trade. This is basic marketing.