The temperature of your entire case is 85 degrees or just your CPU? In either case, if you haven't touched anything for years then it might be time to re-apply the thermal compound, like I said in my last comment.
Might be a good idea to check what's the maximum temperature your CPU should reach when it's put on heavy load.
Last, but not least, is to check if your power supply unit (PSU) is dying. Which might be one of the reasons that your operating system is disabling/shutting down some things, to prevent any damage to the components.
And whats with Thermal paste thing?
Here is a good guide on what is a thermal compound/paste and how to re-apply it easily.