Soldato
What res is your laptop screen, what res is your pc monitor?
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pretty sure a 680 takes a dump on a 760 performance-wise.
http://www.anandtech.com/bench/product/772?vs=854
also 3.4 GHz per core is not that impressive for gaming, you ideally want at least 4 GHz per core on an i5 quad, and they can go much, much faster than that, even just on air cooling.
still, don't see why you are only getting 15fps, something fishy going on there.
try opening up ur nvidia control panel, go to 3-D settings -> adjust image settings with preview -> use my preference -> performance.
this turns off most of the flashy options.
try turning down shadows / AA settings in game too, and see if it makes a difference.
run as many monitoring programs as you can, cpu-z, gpu-z, afterburner, even task manager etc.
you need to try and find out whether it is your CPU / GPU / RAM which is holding you back.
BSOD is normally because of the CPU or even memory problems. Maybe the CPU is getting too hot or the memory is faulty. For 3DMark to crash, something is broken.
Run HWinfo and report back on temps. If they look ok, run memtest86+ and see if that brings up errors. It is a slow test and takes ages but it is thorough.