More than likely an issue with your PC, not Dolphin.
Possible causes off the top of my head, in no particular order.
1. Defective hardware (RAM is the most common hardware related cause of a PC lockup)
2. Unstable overclock
3. Driver conflict\Bad driver
4. Insufficient power supply
More information on the cause would be available in the administrator event viewer in the control panel. The computer should be blue screening instead of locking up, which is the first hint that it is not Dolphin.
Possible causes off the top of my head, in no particular order.
1. Defective hardware (RAM is the most common hardware related cause of a PC lockup)
2. Unstable overclock
3. Driver conflict\Bad driver
4. Insufficient power supply
More information on the cause would be available in the administrator event viewer in the control panel. The computer should be blue screening instead of locking up, which is the first hint that it is not Dolphin.