When you try to install Microsoft SQL Server 2005 on a Windows Web Server 2008-based system, the installation is not completed successfully. Additionally, you receive the following warning message:

SQL Server Edition Operating System Compatibility (Warning) Messages

"SQL Server Edition Operating System Compatibility Some components of this edition of SQL Server are not supported on this operating system. For details, see 'Hardware and Software Requirements for Installing SQL Server 2005' in Microsoft SQL Server Books Online. "

To resolve this problem, download and install the appropriate hotfix:

Windows 2008 32-bit edition

Windows 2008 64-bit edition

Then everything seems to install ok.