Microsoft Dynamics CRM has evolved drastically over the past few years. There have been many updates and versions released, with a range of new features and improvements at each stage along the path. During the upgrade of a Dynamics CRM environment, there are a few points to bear in mind to ensure a hassle- free upgrade process.
I recently had to modify the Activity sub-grid to remove certain activity types from the add activity menu.
Note, this may not be a supported method on how to do this, but there is no documented supported way to so it, so I had to come up with a solution & this worked, in CRM 2013 anyway.