You have accumalated a lot of dust inside the case around the vents of your devices. Take off the side panels and blow it out with a small low power compressor. Do not use canned air dusters as they blow moisture as well as air. If that doesn't work, it still needed to be done. Check the power cord to make sure it is secure. Check the power supply. If you have added a bigger video card or anything that uses more power you need to upgrade your power supply. Most computers these days need at least a 500 watt power supply. good luck