Last week I wanted to develop a program on my PC which needed to use the Collaboration Data Objects 1.21. I thought I had the necessary libraries installed on my PC but one way or another they had disappeared. I quickly found the reason, it seems that after installing Outlook 2007 (and so deinstalling Outlook 2003), the necessary dlls had disappeared. Luckily there is a separate download available for Collaboration Data Objects 1.21 :
Beginning in Exchange 2007 Beta 2 and Outlook 2007 Beta 2, CDO 1.2.1 will no longer be provided as a part of the install of the product. As a result, there is functionality missing that many applications depend upon. CDO 1.2.1 is a package providing access to Outlook-compatible objects through a COM-based API.
There is also another download - Microsoft Exchange MAPI client and Collaboration Data Objects – this version will not install together with Outlook 2007. There also are great articles on MSDN which explain the new ways to access information in Outlook 2007 - What’s new for Developers in Outlook 2007 (Part 1 of 2) and off course Outlook 2007 – What’s new for Developers (Part 2 of 2).