When you are installing VS 2008 or VWD Express 2008 you may encounter failure when Microsoft Web Authoring Component fails to install. There are two known reasons:
1. Setup may encounter conflict with Windows Update on Vista when both setup and Windows Update are trying to access same file. The issue will be resolved in Vista SP1, meanwhile workaround is to reboot machine and attempt setup again.
2. Pre-release Office 2007 software is installed on the machine. Most common case is XPS Document Writer (can be found in the Control Panel). You have to uninstall any pre-release Office 2007 pieces since HTML designer in VS 2008 includes Office 2007 RTM components and hence is not compatible with Office Beta bits.
WAC setup logs can be found in the TEMP folder, they are named as setup*.log. If you sort files by date, you should see most recent ones and can peek inside for more technical information. If you are going to submit a bug or need assistance, please attach .log file to the bug in Connect or, if you are seeking help in ASP.NET forums, please list error code and error message from the log file in the forum post.