There's about nine hundred thousand different things that can throw an ntoskrnl.exe error. That stands for NT (Windows NT, which used to be a server platform but is now the basis for most windows file systems.) OS (Operating system) KRNL (Kernel, or the core of the OS. So basically, Windows NT operating system kernel executable error is what that is and just about any service or application running could cause a problem with it.
I would start with running Seatools for windows to see if it's a hard disk error. Hard disk failures often result in errors as do failing memory modules. Run the short DST test and if it passes, run the long generic. If it passes that run memtest86 for a minimum of 4 and preferably 7 passes on each module. Test the modules separately as testing multiple modules can result in false errors plus you can't really determine which module is throwing the error if tested together.
If the hard disk and the RAM are both ok after testing we can move forward. You might also run an sfc/scannow to see if the bsod is a result of a system corruption.
Seatools for windows:
http://www.seagate.com/support/downloads/item/seatools-win-master/
Memtest86:
http://www.memtest86.com/download.htm
SFC/Scannow (Ignore that the tutorial is for windows 7, it's the same test:
http://www.eightforums.com/tutorials/3047-sfc-scannow-command-run-windows-8-a.html