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Hi I also have an M70 on a D/Dock station and I run a 24" DVI LCD HP monitor and I can assure you, you can UNDOCK quite safely and get your screen back as I have played these games myself. The system does prefer to either be put into standby or turned off before undocking, but sometimes you have to HOT UNDOCK as I run multiple hardware which sometimes causes me problems which then reverts me to having to HOT UNDOCK.
When you have undocked the machine and end up with a bleack screen all I did which worked pukka for me was hit the Function (Fn) button together with the F8 and this will bring up 3 pictures (bottom right handside) which will take you through either having laptop external monitor or both together each click of the buttons will take you to the next choice. If this fails to work try the following keys Alt button together with your enter button and this SHOULD wake up the laptop screen.
If this fails hot dock and use Fn and F8 to just give laptop screen then hot undock, this sets the Nvidia card up ready for the loss of a screen. Hope this works it did for me good luck.