I have completed two more flights from KSEA to KSFO, after installing 24 GB of RAM, replacing my 9 GB.  I tried using fairly high graphics settings to see when it would fail.  Using Process Explorer, the VAS was 4,104, 800K when it failed.  On the most recent flight to KSFO, was able to do a successful auto landing, taxi to the gate and shut down, but then it said out of memory with VAS 4,092,880K.  So the reply posted earlier is correct in that it appears to fail when VAS is just over 4,000,000K no matter how much memory is installed.  However before upgrading the memory it give OOM when the VAS was only 3,178,204K and 3,124,076K.  Not sure why this occurred, but OOM failures appear less likely than before adding the 24GB memory.  Using CPU-Z it confirms that I have 24 GB of memory.  However, using Control Panel, System, it says I have 24 GB of memory, but only 16 GB usable.  At any rate, I can now fly the 777-200 with all four monitors, using real world weather (have not tried Active Sky yet), with Plan-G on another networked computer, CH yoke and rudder pedals, and Butt Kicker enabled.  So I don't plan to revert back to Windows 7.  One issue with Windows 10 is that my 'Factory Overclocked' i7-920 will now only run a 2.67 GHz, rather than at 3.2.  On the Alienware forum others have experienced similar issues, even after upgrading the BIOS.

I hope this info is helpful to others who are considering upgrading to Windows 10.

Jim Kaye  :) :)