Have you burned the image to disc? There is a setup.exe right in the home directory. You can try the web downloads if you are having trouble with the CD install.
I've tried the same thing. I also downloaded the vcssetup.exe file, but it only directs me back to the website to download the orca file.
How do you get the setup.exe file out of the img file?
From the Visual Studios 2008 beta 2 Downloads page, I have copied some of that information here:
Some software burning programs allow you to "burn" to a folder instead of an actual recordable CD or DVD. This might allow you to install it that way since you should see a setup.exe file there.
I hope this helps.
Download a product called Daemon Tools - http://www.daemon-tools.cc/dtcc/announcements.php
This is a free CD - DVD emulator. Once you install it you can point it to the .img file you downloaded. Your windows explorer will now think that the .img is actually a cd or dvd and you can treat it as such. Just go to the new 'drive' and either click on setup.exe or right click it and autoplay. I do this quite often with beta software that I don't want to waste a cd on. I am running XP with SP2. I don't know how this will work under Vista. Also, if you are running Vista, remember that it runs under the least privilege model and you may not be able to see or run things without elevating your user status.
Hope this helps. Just remember 'Programming is an art form that fights back.