If you have tried to install VS2005 August CTP on Windows Vista 64-bit edition you probably found out that it is not possible to do because 64-bit .Net framework fails to install. The reason it fails to install is quite silly. It's a bug in the launch condition in the installation package.

Here is how to get around this. You will need the msidb.exe tool found in the bin directory of the Platform SDK

1. Create a temporary directory and copy \VS\WCU\dotnetframework\x64\NetFX64.exe from the Visual Studio DVD into this directory. Copy msidb.exe into the same directory (or ensure that it is in the path)
2. Explode it using a command
   NetFx64.exe /Q /C /T:%CD%
3. Extract the LaunchCondition decriptor by running:
   msidb -e -dnetfx.msi -f%CD% LaunchCondition
4. Use notepad to edit LaunchCondtion.idt. Add OR (VersionNT=600) to the condition as shown below:
   (Version9X >= 410) OR ((VersionNT = 500) AND (ServicePackLevel >= 3)) OR (VersionNT = 501) OR ((VersionNT = 502) AND (ServicePackLevel >= 1)) OR (VersionNT=600) [LocProductName] is not supported on Windows 95, Windows NT, Windows 2000 without Service Pack 3 or greater, and Windows Server 2003 without Service Pack 1 or greater.
5. Use MSIDB again to import the updated launch condition:
   msidb -i -dnetfx.msi -f%CD% LaunchCondition.idt
6. Now launch install.exe and complete the framework installation. At this point you can relaunch Studio setup and successfully complete it.