Congrats if you have successfully installed Dynamics CRM4.0. Now everything works cool apart from this bug that occurs when you click on System Settings:
an entry with the same key already exists
But well, it’s a simple issue, you just need to update your CRM to the latest rollup.
Link to solution: http://support.microsoft.com/default.aspx?kbid=2449283
Just make sure you always keep your CRM up to the latest stable version. 🙂