|When you re-installed did you install or update all your drivers?|
People forget to install key drivers after doing a re-install.
Key drivers include the most important which is the chipset drivers.
Other key drivers would be video, audio, and Network drivers.
Often the drivers provided by the native OS (for the chipset) are basic minimum capability drivers to get you going. However you need to then install the chipset drivers for optimum performance.
Read more about shut down issues here:
☺ When everything else fails, read the instructions.