...dunno, Crash...
I would have thought that after all the FS Data has been loaded into your on-board Memory, the actual Sim would be sharing Windows, along with everything else, loaded off of your C Drive?
If you have sufficient Memory installed, everything will be running from there...not the Hard Drives?
Paul....

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P.S. ..once everything has been loaded into Memory, my Hard Drive light rarely comes on...

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The only advantage I can see....If your main C Drive crashes, you still have all the FS Data stored on the Spare, Second Drive?
Win XP Pro....2.3 GB of Memory.
Win 8.1 64-bit. DX11. Advent Tower. Intel i7-3770 3.9 GHz 8-core. 8 GB System RAM. AMD Radeon HD 7700 1GB RAM. DVD ROM. 2 Terra Byte SATA Hard Drive. Philips 17" LCD Monitor. Saitek Cyborg X Fly-5 Joystick. ...and a Briggs and Stratton Petrol Lawn Mower.