The Microsoft Dynamics CRM 5.0 Connector for SQL Server Reporting Services must be uninstalled before Microsoft Dynamics CRM 2013 Reporting Extensions can be installed.

The error occurred when I was trying to install the reporting extensions for a new CRM 2013 demo instance as you cannot import an existing organisation without the reporting extensions.

Unfortunately there is no way around this (that I have found) and for the demo purpose I installed SQL on the same box as CRM.