After installing Visual Studio 2010, I started getting an error message every now and then when I would try to view the designer in Visual Studio 2008.

The first popup would say:

The operating system is not presently configured to run this application

Which was followed by the message:

Cannot load MSO.dll

I found that mso.dll was located in “C:Program FilesCommon Filesmicrosoft sharedOFFICE12”, and after adding that path to my PATH environment variable in Windows (I’m running XP Pro) the issue seems to have gone away in VS2008.