Correction... not necessarily triggered by afk.  I thought it was, but just got a blue screen while I was actively playing.  I'm now 6 hours, and 5 shutdowns into the game, 4 of which happened while I was afk, and 3 of which were blue screens.  Again, if there's more info I can provide that will help diagnose and fix the problem, I'd be happy to help... or if someone has had a similar issue, if you could point me to the fix, I'd appreciate that too.  I updated my drivers after the first blue screen, as I understand that can often cause those issues.

Update...   NO I don't use many custom designs, I've made 2 so far, just cus I wanted another survey ship, that doesn't seem available in the premades. Yes, I updated all my drivers, I did uninstall and reinstall.  I thought this fixed the issue, got about 90 min into a game, and another blue screen.

If something makes your computer unintentionally boot you might have a hardware issue. If that only happens under conditions of heavy load (like in games), for example your power supply could have a problem.
Once I had an Enermax power supply which worked great for nearly a year, but then reboots began to happen in 3D games. Otherwise the machine continued to run perfectly, so I was suspecting the graphics card first. But eventually replacing the power supply fixed it.

Of course there are other possibilities, hardware-wise. I'm just pointing in that direction because it's quite hard for a software error to force a contemporary operating system (like Windows 7) to reboot. Even if your NVidia driver falls flat on the face it'll rather try to reset itself than tearing the whole system down.

Oh yes, memory...! memtest86+ really is a good thing, try that! And give it enough passes.

if anyone following this thread cares... I'm gonna be formatting my HDD in the next couple days, and reinstalling windows fresh...  I like to do this every 9 months or so anyway, my computer seems to work so much better after I do each time, and it's well past that... I'll post again after I've had a chance to back up, reinstall, re set up, and test the game...

After a few issues reinstalling windows... Lost my disk, barrowed a disk from a friend, which ened up being the wrong version... anyway... now that my computer is up and running again, game seems to be working fine.

Donagh55, you deserve an award for perseverance.   I'll give you a karma point for patiently explaining your tribulations so that the developers can make a better game.