Hi observatory & welcome to the forums ^_^,
I have analysed your dump files and below has been provided an analysis of the same for informative purposes :-
This is a very common bugcheck. Usually the exception address pinpoints the driver/function that caused the problem.
The callstack has captured the driver responsible for the crash -
And it is your ATI driver which is causing the problems according to the dump file.
0: kd> knL
# Child-SP RetAddr Call Site
00 ffffd000`25b7e370 00000000`00000000 atikmdag+0xc50ab
Kindly uninstall the currently installed ATI driver using the Display Driver Uninstaller from this **LINK**. Once you have uninstalled the current driver, do a system restart. After booting up, install the driver from this **LINK**.
Let me know how it goes ^_^