SSMSE Error: Package 'Microsoft SQL Management Studio Package' failed to load

On Windows 8 (64-bit), after installing SQL Server 2008 R2 SP2 and installing SQL Server Management Studio Express, I could not get SSMSE to start up successfully - the IDE would open up with the following pop-up dialog error:

and then shut down when I click 'OK'

After scouring the web for a solution and unsuccessfully trying various suggestions, I eventually got to here: Duncan Smart's weblog; I was astounded when his very simple solution fixed my problem.

Fix: is to remove or rename this Registry subkey and then restart SSMSE:

HKEY_CURRENT_USER\Software\Microsoft\Microsoft SQL Server\100\Tools

For example rename the sub-key '100\Tools' to '100\Tools-old' or any other name.
e.g.

HKEY_CURRENT_USER\Software\Microsoft\Microsoft SQL Server\100\Tools-old

Then re-open SSMSE and it will re-create this sub key and will start up successfully (after it displays a pop-up message about 'initializing the environment for the first time' or something along those lines).  

Wow!