This post will be entirely useless to you, until you encounter this same problem and remember that you read this.
I was recently building out a new developer image for Vista. I have all of my ISO files for installing large programs such as Visual Studio Editions, SQL Server, and the like, stored on a handy external hard drive. One of my first tasks is to install an application that allows me to mount images. I have been using Virtual CloneDrive lately. I have really liked this tool, especially since it allows you to just double-click an ISO file and off it goes.
I used Virtual CloneDrive to mount a couple files and those installations went fine, including VS 2008 . I then proceeded to an ISO for VS 2005 Team Edition for Software Developers. I have used this ISO many a time before, not on Vista however. However, this time the setup could not access certain files. After some digging, I found a forum post about similar issues, and another post on a possible solution. It seems that Virtual CloneDrive is not completely compatible with Vista, at least for some ISOs. The solution was to uninstall, and use Daemon Tools instead. I tried, and sure enough, the installation worked fine with Daemon Tools.