One of the most accepted bits of conventional wisdom among pundits as 2007 draws to a close is that the marketplace has rejected Windows Vista in favor of Windows XP. The biggest piece of evidence is Dell’s decision in April 2007, based on a vocal response via its Dell IdeaStorm page, to continue offering Windows XP as an option on some consumer systems. It picked up steam with Microsoft’s announcement in September that it was going to allow its large OEM partners to preinstall Windows XP until June 30, 2008, a five-month extension over the original January 30 cutoff date. (A CNET News report from last April indicates that HP and Lenovo have adopted similar strategies, offering XP as an option on business-class machines but for consumer products.)

Both of those moves got a lot of press, but proof about how either decision has actually played out in the marketplace is, unfortunately, pretty thin. Microsoft doesn’t break out its mix of Windows shipments with this level of detail. OEM computer makers are tight-lipped as well. And if any third-party market research firms have done any studies on this subject, they have yet to publish the results.

But I stumbled on an unexpected source of data that has helped me get a much better picture on what the actual numbers might be like. As it turns out, Dell has published a large database of information about its current inventory for anyone to see, and I was able to sift through it to form some surprising conclusions about the current relationship between XP and Vista in the PC marketplace. The short version: Consumers have embraced Vista overwhelmingly, whereas small business is much more reluctant, preferring XP by a better than 2-to-1 margin.