process failure

my friend pc suddenly started crashing and restart repeatedly when i checked the processor golden foil color seems to be faded any ideas hot to clean it or repair it? https://ibb.co/5kYwM0r

My brother bought a pre-built pc which run a gt 640 fine for 4 years and never have a problem but recently he want to buy a new graphic card.So i think gtx 750 ti is a good option to go with but im a bit worry about PSU as didnt have a voltage as recommended for 750ti So if i replace a gt 640...