Well, you've left a lot to consider. Have you checked that the case and CPU fans are running? Where do the unit sit? Units that are placed inside computer desks that have doors in front of them are just begging for overheating problems as there is very poor air ciculation. Is the CPU sitting on the floor? Here the enemy becomes dust and dirt. Dust and dirt are the most common causes of PC heat issues. The CPU heat sink becomes clogged with dirt and cannot cool effectively. Use canned air (available at most stores that sell PCs) to blow out the heat sinks. DO NOT REMOVE THE HEAT SINK/FAN ASSEMBLY unless you have proper thermal paste to apply for the remounting. Usually a good cleaning is all most machines need.