Prevent Visual Studio from automatically creating "Mixed Platforms" solution configuration

How do I prevent Visual Studio 2008 from automatically creating the "Mixed Platforms" and "Any CPU" solution configurations? We have "Win32" and "x64" configurations and a developer needs to choose between them. However, as soon as anyone makes any changes to the solution VS automatically creates "Mixed Platforms" and it seems to be the default configuration. This causes a lot of issues, because it turns out some new projects are not selected in this configuration or the wrong project configuration is selected, etc. I just want to stop it doing that and manage the solution configurations myself.

We see a similar issue with Visual Studio 2005 projects that we want to build both for a Win32 configuration and for a number of distinct smart device platform/configuration combinations.

At arbitrary times, every configuration gets auto-generated for every platform, whether it's valid or not, exploding the size of each of our ~50 project files and causing a lot of work to fix the issue.

It consistently happens when we open the Configuration Manager dialog, and it sometimes (but not always) happens when changing a project setting for a configuration. In the latter case, it seems to be related to manipulating the platform and configuration drop-downs on the project setting dialog.

We filed it as a Visual Studio issue; MSFT closed it as "won't fix".

I've been dealing with the same sort of problem. I agree it is a mess. I've seen two viable options for dealing with it - neither are really what you want.

1. Manually remove the configurations that it creates by going to the configuration chooser and picking edit...
2. By default (at least if I start with a fresh solution in VS 2010) and start creating new projects (both class libraries and apps), you end up with Any CPU, Mixed Platforms, and x86 for your Solution Platforms. Visual Studio seems to do a good job adding new class libraries to both Any CPU and Mixed Platforms (since they default build for the Any CPU target) and adding new apps to both Mixed Platforms and x86 (since the default build for the x86 target), and putting both new class libraries and new apps to Mixed Platforms. So Mixed Platforms ends up being a nice default since it builds everything. I'm not sure why it's not adding new projects for you to Mixed Platforms

You could filter your .sln files in a commit hook of your source control. So that if you check it in the .sln file and possibly the project files get fixed. The open source Chromium project has such a filter implemented.