I heard from a customer last week who was trying to install the final release of Visual Studio 2005 but could not even launch the setup program. They ran setup.exe at the root of the installation DVD, and a small dialog appeared stating that setup was copying files to the %temp% directory, and then it started loading installation components. At this point, setup hung and the progress bar never reached 100%. In this scenario, the log file %temp%\dd_vsinstall80.txt had the following information as the last entry in the log before setup hung:
[12/17/05, 11:11:11] setup.exe:  ISetupModule::SetManager() failed in ISetupManager::LoadSetupObjectGuid() : vs_setup.dll
In this scenario, as well as in a few other cases listed in this forum post, the underlying problem was traced to the Kaspersky anti-virus program being installed on the system. If you see VS 2005 setup UI hang when trying to launch setup, please try to uninstall Kaspersky and hopefully it will resolve the hang for you as well. Please note that we have seen that simply disabling Kaspersky has not seemed to help, and that you will have to perform a full uninstall of this program to workaround this issue.
If this workaround does not work for you, please try to use the steps in this blog post to enable verbose MSI logging and then reproduce the hang and send me a zipped copy of the most recent file named %temp%\msi*.log so that I can try to take a look and see if I can figure out a root cause and workaround for you. I have seen a few other random cases of setup UI hanging like this, and most of them can be diagnosed with this verbose log file.