- While OS X is running, insert your OS X Snow Leopard Install DVD.
- Double click Install Mac OS X.
- Keep the DVD inside your computer while you wait for it to restart.
- Wait until the second phase of the installation procedure completes.
- You are now downgraded to OS X 10.6.2 (or something less than 10.6.6).
- Download and apply the OS X 10.6.6. combo update to bring you back to 10.6.6.