Very often during development we try to remove an assembly from GAC. However, due to many reasons the assembly might not get deleted and the above screen is displayed. There is no easy way to remove this assembly as it may be locked due to numerous reasons and one might need to break his head identifying the proper reason behind this.
However, there is an easy solution to this problem.
Open “regedit” and navigate to “HKEY_CLASSES_ROOT\Installer\Assemblies\Global”. In this location one can find the list of all the assemblies which are registered in GAC. Delete the appropriate entry from this list. Now you can delete the assembly from GAC as well. This is a simple trick to get rid of that stubborn assembly which was stuck in your GAC.
I hope this simple trick will save many man hours !