This can be a bit tricky … and you can either get enough exposure by doing it so many times that you just know what needs to be installed before you start, or you can get through a bunch of steps in the setup before it stops to tell you that the right things aren’t installed and can’t continue.
Exchange 2010 requires Windows Server 2008 or Windows Server 2008 R2. You can use Server Manager to install the Web Server (IIS) role, however, there are many, many pieces to IIS that are broken out into individual components in 2008. Which ones are required to get you the prerequisites you need to get through the Exchange 2010 installation?
Instead, consider using ServerManagerCmd.exe, which is built-in in Windows 2008 to automate the role installation for you. This command is very useful in installing new components and making sure that you have the pieces you need. From a command line, run:
ServerManagerCmd -i RSAT-ADDS Web-Server Web-Metabase Web-Lgcy-Mgmt-Console Web-ISAPI-Ext NET-HTTP-Activation Web-Basic-Auth Web-Digest-Auth Web-Windows-Auth Web-Dyn-Compression RPC-over-HTTP-proxy Web-Net-Ext –Restart
This will install the necessary components including ADDS which needs to be installed for remote administration of Active Directory and for the Exchange 2010 schema extensions to be installed. Once the command completes, the server will restart. After that, you’re ready for your Exchange 2010 installation.
You can find more information on ServerManagerCmd.exe on Technet.