Swollen Filter Cap
Usually if a switch power supply (especially the computer power supply) connected with a wrong ac voltage especially the 110volt power supply with 220 vac input, the filter cap will burst and swollen. You could also see the smoke before the fuse break. Generally what you need to do in this kind of problem is to check the fuse, bridge rectifier and of course the big filter cap. In certain cases the Varistor may blows too. If the fuse has turned into dark color and the filter cap did not burst, what you need to check is the bridge rectifier, power ic and the power fet. If the power FET is shorted then you should directly replace the power ic and check the surrounding components too. Rarely it will cause the secondary diodes to go shorted. In order to avoid such problem make sure the power supply switch is properly selected.