Blue screen of death is a condition when your computer suddenly stop working and a blue screen appears on the screen having some text written on it. It happens because of either hardware failure or some crappy software. According to Wikipedia article
The Blue Screen Of Death (also known as BSoD or bluescreen), known officially as a Stop Error or a bug check is the error screen displayed by the Microsoft Windows family of operating systems upon encountering a critical error during system startup, of a non-recoverable nature, that causes the system to “crash.” The term is named after the color of the screen generated by the error.
In PC, most probable reason of rebooting of PC is either malfunctioning device drivers and kernel modules. Kernel modules error lets PC to reboot therefore mostly either drivers or software are responsible for BSoD. WhoCrashed is a free application that tells you exactly which software, or device driver is a reason for error. You can uninstall the software and update drivers after watching the report to overcome the problem.
For example in the above given screenshot, you can see that it shows the name of software as well as error and file path which causes the problem. According to makers of this tool, this software is not always 100% sure about the drivers responsible for the crash, but most of the time it gives the accurate result.
Download Whocrashed to know about bad software and drivers which causes error in your PC.