Error corrupt cab file, 80200053

I'm working with Vista Ultimate and am trying to install Visual Studio 2005
service pack 1, then the Vista compatibility update for VS. Every time I try
installing the software I'm greeted with a "error in data cab file" message.
Visual Studio was properly installed and I've even uninstall/reinstalled the
program to make sure.

I've tried installing directly from the website as well as running the
installation after the file has been downloaded to my HD (that is, the file
shouldn't be corrupt).

If it helps matters at all, Windows Update also downloads the service pack
and attempts to install the file, then gives me error code 80200053, a code
which hours of scouring has turned up zilch.