Hello,
Unfortunately, Visual Studio Express editions are limited, and do not support neither MSTest (which is a test runner from Microsoft), nor the ability to load add-ins, which is required to run Isolator in Visual Studio.
TestClass is a part of MSTest, and it doesn't exist in Visual Studio Express.
You could try using NUnit to write and run your tests, and run them manually using TMockrunner like this:
TMockrunner.exe nunit-console.exe yourtestproject.dll
It would be much easier, however, if you could use another version of Visual Studio. You can download trial versions of Visual Studio Ultimate here:
http://www.microsoft.com/visualstudio/en-us/try
