If you're installing SQL Server on your Vista Business/Enterprise or Ultimate machine chances are you do intend to use it for development purposes and obviously have already installed IIS. But chances are you might receive a warning message on the System Configuration Check page of the SQL Server 2005 Setup.
"Microsoft Internet Information Services (IIS) is either not installed or is disabled. IIS is required by some SQL Server features. Without IIS, some SQL Server features will not be available for installation. To install all SQL Server features, install IIS from Add or Remove Programs in Control Panel or enable the IIS service through the Control Panel if it is already installed, and then run SQL Server Setup again. For a list of features that depend on IIS, see Features Supported by Editions of SQL Server in Books Online."
Do not cancel setup to install the missing features in the hopes of re-installing SQL Server again. Cause I did and to find out that SQL Server (more particularly the database services) wouldn't install. You can simply install the required components without canceling the setup and resume it. I've tested that it works.
Let's first see what are the required IIS components that SQL Server depends upon. Well there's a KB article that has the official word on the components you'll need. If you prefer a more graphical illustration refer to the images below:
That's it, resume the setup. You'll notice that the setup again detects your IIS configuration and will continue and will finish without any problems. But what to do if you canceled the setup and ended up on this page via a search engine. Well the solution is fairly simple.
What happens in a re-installation attempt is that the setup determines that you already have SQL Native Client installed on your machine and doesn't extract the MSI package which unfortunately is a very-very important package. So to successfully re-install SQL Server 2005 you must uninstall all of the 4 entries you find in your Add/Remove Program Control Panel Applet bounded in the yellow rectangle in the image below.
Note that you may not have all four items on your list, the item just above the rectangle is of course not on your list as it didn't install successfully. Although you don't need to but I recommend reboot and when run the setup again you will be able to install SQL Server to seamlessly work with IIS.