You should look on your motherboard and check if there are any bad capacitors. Before a capacitor gets fried it begins to swell and even to leak. Look also for burned chips on your MB. Capacitors can easily be changed, they have tech specifications written on them and you can buy new ones.
Another thing you should do and i think THIS is gonna solve your problem: check the thermal paste!! See if the paste has become solid and change it with a better one. I reccomend Arctic Silver 5 - High Density Polysynthetic Silver Thermal Compound.
Tell me how things go after you do this.
Best of luck mate!