Resently, the computer has shut itself off, is this related?
yes. as brett74 already suggested, clean out the case and all heatsinks and fans. visually inspect the motherboards circuitry. look for burnt, or "toasted" components (golden brown components). also look for impregnated or leaky capacitors, specifically the ones close to the CPU heatsink. impregnated capacitors will be bulging, either from the top or the sides or both. correctly functioning radial cylindrical capacitors will have a perfectly flat top.
until the problem has been found, i strongly recommend
NOT powering on the computer as it may present a fire hazard.
