Installing Exchange SP1 Pre-reqs on Windows 2008
Prereqs:
 
.NET Framework 2.0 or 3.0
Powershell
MMC 3.0 (Installed by default)
IIS 7.0 with various components
Unlike IIS 6 in Windows 2003, the version that comes with Windows 2008 are broken down into many different components that must be installed/selected individually during the installation process. You can install this through the Server Manager MMC using Roles or use a command line as described here.
 

NOTE: All server roles other than the Edge Transport server role must first join to the appropriate internal Active Directory forest and domain

Steps:

At the command prompt type:

ServerManagerCmd -i RSAT-ADDS

This will install the Remote AD Management tools, it is very important that this is installed PRIOR to installing IIS 7. The system will prompt to reboot. Please do so.
 
After the reboot, at a command prompt type in the following, everything must be typed in the correct order: 

ServerManagerCmd -i Web-Metabase
ServerManagerCmd -i Web-Lgcy-Mgmt-Console
 
Installing Powershell:
 
ServerManagerCmd -i Powershell
 
Installing IIS requirements:
 
ServerManagerCmd -i Web-Server
ServerManagerCmd -i Web-ISAPI-Ext
ServerManagerCmd -i Web-Metabase
ServerManagerCmd -i Web-Lgcy-Mgmt-Console
ServerManagerCmd -i Web-Basic-Auth
ServerManagerCmd -i Web-Digest-Auth
ServerManagerCmd -i Web-Windows-Auth
ServerManagerCmd -i Web-Dyn-Compression
 
Optional (if server will be supporting Outlook Anywhere, RPC over HTTP install the following component)
ServerManagerCmd -i RPC-over-HTTP-proxy
 
Congratulations, the system is now ready for Exchange 2007 SP1 install, just pop the CD in and run the installation. Good luck.