I can not find a service manual for this or a similar machine. I also can not find any reference to a teardown procedure for your laptop you will need to contact Medion customer support and ask them for the service manual or instructions on how to teardown the laptop.http://www.medionusa.com/
You will need to open up the laptop blow out the dust and clean the fins on the heatsink(s) from any foreign objects, such as dust or hair. Then you will need to remove the heatsink(s) and apply thermal paste. The procedure for doing that is here. I use and recommend Arctic Silver 5 thermal paste. You can purchase that here. Then reassemble the laptop. If this doesn't resolve the heat issues your GPU is going to need to be reflowed or it's BGA reballed. Proper reflowing usually works. Make sure who ever you have do it uses no clean flux in the procedure. After resolving the heat issues. When you get the laptop running hit f8 as the computer is starting up, you may have to hit it a couple of times. This will bring up a boot menu choose Last known good configuration. That should get rid of your windows explorer error.