Where are the Windows Server 2003 sites hosted?

Some people expressed surprise that there could be thousands of sites running on Windows Server 2003 before it went on sale. The main reason for this is that some shared hosting providers who were part of the Windows Server 2003 beta program were prepared to run part of their sites on Windows Server 2003 prior to launch. The three providers with the largest number of active sites on Windows Server 2003 are all Microsoft Certified Partners while the fourth largest is Microsoft itself. No one else had more than 1000 active sites running on Windows Server 2003 at the start of May.

Top Microsoft Windows Server 2003
hosting companies by Active sites, May 2003
CompanyActive Sites
  Interland4,996
  Schlund3,125
  Fasthosts2,250
  Microsoft811

For comparison, Schlund and Interland [primarily due to its acquisition of Dialtone Internet] are also two of the largest Linux hosting providers, along with specialist Linux hosting providers Rackshack and Alabanza.

Top Linux hosting companies by Active sites, May 2003
CompanyActive Sites
  Schlund1,450,868
  Rackshack234,740
  Alabanza150,180
  Interland144,488
  About118,287
  Valueweb109,998
  Verio102,696