I find this report very hard to believe and the results must be seriously skewed somehow, but IDC have a report called Server Watch, which apparently shows Windows server boxes outselling Unix boxes in 2005 (by $17.7bn to $17.5bn).
Not unexpectedly, in terms of web server software market share Apache still dominates the market running on more than 3 times as many web servers as Microsoft IIS, has has done so consistently since the mid 90’s with no signs of Microsoft even getting close. Although this server survey is just a web server survey, this makes me question the usefulness of IDC’s report of server sales – does this include various Linux flavours, and since being free, are they included in IDC’s report? Probably not. So in terms of sales Windows servers may be leading Unix, but in terms of installations I have no doubt that there are more Unix based server installations in the wild than there are Windows, and I doubt even Microsoft would argue with that.