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#11
chances are the issue was caused by your psu. its so close to the recommended requirements of the card it was probably pulling at almost 100% the entire time.
that and it being a prebuilt computer means the psu was probably a cheap chinese jobby. (you can normally tell as theyre just a generic metal grey colour).
almost all pcs take an atx powersupply. its only in extremely small pcs and or flat cased types (where the monitor sits on top) but the fact you have a gpu means its not the case.
changing a psu isnt as hard aa youd think. a quick search on YouTube will throw up dozens of how to vids :)