Also: VERY IMPORTANT to run the built-in diagnostics before anything else. This alerted me to the fan connector not being firmly seated (push DOWN not IN). Power up and immediately hold the D key until you see the diagnostic screen.
Mine came with two 8GB modules. One is failing memtest86 so I am replacing them with two 16GB SO-DIMMs. If you got to System Settings > General > About, it will tell you what's in there.
