Is this the download link you are using:
Link Removed
Also located this:
A few suggestions/comments on the setup process:
1) Before starting the SP1 upgrade make sure you first uninstall the standalone VS 2005 Web Application Project download if you've installed that on your system. You'll no longer need this as support for it is built-in to SP1, and the SP1 installer will block and make you uninstall it if you have it installed. Your existing web application project files will continue to work just fine - so you won't need to-do anything to update them to work with SP1.
2) SP1 will run the upgrade patching process on each copy of Visual Studio 2005 it finds on your system. So if you have VS 2005 Professional, Visual...