ADO (ActiveX Data Objects) is a system to access databases by Microsoft. To work with databases via ADO, you need to have ADO 2.1 or above installed on your computer. ADO 2.1 or above is usually installed by default in Windows 2000 or above. It can also be downloaded and installed from Microsoft web site.
You can check the ADO version in Reportizer by choosing Help | About... menu (System info tab).
To connect the database via ADO, choose the corresponding tab when selecting your report database.