I attempted installing Visual Studio 2008 I got an install failure when the Microsoft Visual Studio Web Authoring Component was being installed.  I found several postings on the Microsoft Support Site (http://support.microsoft.com).  After reading those posts here is what I have found:

1. Uninstall ALL Beta everything
   1. SDKs
   2. VS Add-Ons
   3. Development...whatever
2. Uninstall Microsoft Windows SDK 6
3. Reboot and attempt VS2008 installation again

I also uninstalled Sharepoint Designer, as I have seen issues with this before, but it does not appear that this is not an issue/problem source.