Visual Studio 2008 installation problems
Web Authoring Component can fail during Visual Studio 2008 setup if Microsoft Expression Web Designer Beta 1 is installed.
One of the prerequisites for Visual Studio 2008 is the Visual Studio Web Authoring Component.
If this component fails to install it might be because some beta parts of Office 2007 is installed.
If you don't have anything named Office 2007... in "Add or Rem Programs" try to see if you have Microsoft Expression Web Designer Beta 1 installed. If you have Microsoft Expression Web Designer Beta 1 uninstall it and now Visual Studio 2008 will install without problems.
If you can't imagine what Office 2007 beta stuff you might have try to examine HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Office\12.0 subkeys to find out what application might be causeing the problem.