You recently bought a Medion multimedia PC system MD8365 when you plug it in some lights come on and a fan goes on for five seconds then nothing. Are you recieving any beep codes when you turn it on? Please disconnect power cable from wall outlet and from that computer.
Press a power button for one minute. Plug back power cable into wall outlet and into back of that computer. Power it on and see if it will boot properly.
Is that computer still under warranty? If so, I can try to find warranty support for you. I want to to make sure that computer is not under warranty so that we don't void a warranty.
You can contact Medion technical support at their toll free #866-633-4660. Customer care is available absolutely free during your limited warranty period. It will help for you to get a serial number or product number off a back of that computer.