Problem: Double clicking on .sln file does not open the solution in Visual Studio.
Solution: This may happen if you have some version control system installed, especially Clearcase. This is a problem with the extension-application association. If you right click on .sln file, you will see that the application associated with this extension is ‘Microsoft Visual Studio Version Selector’. Change the association to devenev.exe. You can find this executable under <Visual Studio installed directory>\Common7\IDE.
Next time when you double click on .sln file, it should open it Visual Studio IDE.
Note: This solution works for Microsoft Visual Studio 8 / 2005. This has not been tried on any other version.