If, during installation, you are not connected to the Internet, use this checklist to ensure you have the necessary prerequisites installed prior to installing Exchange Server 2007. These checks are done automatically when connected to the Internet during installation. By completing this checklist, your system will be better prepared to deploy Exchange Server 2007.

http://www.microsoft.com/technet/prodtechnol/exchange/2007/deploy/prereqs.mspx?wt.svl=preparing