I had some problems when installing Expression Encoder 2.0 (Available through MSDN or download Expression Encoder 2.0 Trial) on my Windows Server 2003 with Service Pack 1. It kept on nagging about an incorrect version of Windows Installer.
Setup requires a minimum Windows Installer version 3.1.4000.2435 and detected version 3.1.4000.1830. Please update your system and run Setup again.
But when you look for the latest version of Windows Installer you will find this one - Windows Installer 3.1 Redistributable (v2) which will not install on Windows Server 2003 SP1. Instead use this one - Update for Windows Server 2003 SP1 Service Pack 1 (KB898715). Restart your server and continue installing Expression Encoder.