Hello Saraph. I am actually having the exact same issue you are having, with an identical laptop (GT70-0NC), upgrading from a GTX 670m to a 770m, bought from the same seller as you on ebay. I have tried 3 vBios versions (stock, and the two posted here), and multiple Nvidia drivers, both with and without modded .inf files. In my case, I'm noticing that with the 80.06.54.00.11 vBios I get a BSOD when any program attempts to access the 770m, and this is with any Nvidia driver installed. I've also noticed that before the BSOD, even when idle, CPU usage will spike to 100% for a brief moment on a random thread every half second or so, bouncing around like mad. Disabling the 770m through device manager seems to stop the CPU spikes, as well as the BSODs, but obviously isn't a great solution. There has to be a proper solution to this somewhere, as I really don't feel like returning a card that otherwise seems to be functional. Any help on this would be immensely appreciated. Thanks!