When I set my active solution from Win32 to x64, I cannot build the project or view the properties.
When I try to build my project, it is skipped.
When I try to view the properties, the first time I try, nothing happens. The second time, I get an error message saying, "The operation could not be completed. Unspecified error".
I am running Visual Studio 2008 sp1.
The project compiles correctly on another computer.
The x64 components for Visual Studio 2008 had not been installed on the second computer. Installing those solved the problem.
(There are a lot of unhelpful hits in Google when searching for a solution to this problem. Hopefully this helps someone else in the future.)
In my case removing TargetFrameworkVersion attribute from VisualStudioProject xml node of vcproj file solved the problem. I suspect it was caused by project file conversion from previous version of Visual Studio.
VS 2008 Pro doesn't install the 64-bit compiler and tools by default. You have to explicitly select them during the installation.
Control Panel -> Uninstall Programs. Select Visual Studio and click Uninstall/Change. Wait. Wait some more. Click Next. Choose Add or Remove Features. Expand MSVC 2008 -> Language Tools -> Visual C++. Select X64 Compilers and Tools. You'll probably need your original installation media.
Once the 64-bit compiler and tools are installed, you should be able to add a 64-bit configuration to your solution
Even if Visual studio 2008 64 bit is not installed in windows 7 machine, User can select compatibility mode to windows xp using property option and can continue to run visual studio using "Run as administrator" option to avoide this error.
I had the same issue with Visual Studio 2005. I fixed it by running Visual Studio install/repair and selecting the 64 bit components under the C++ install options.
