video card make normal screen turn to pink screen

my Gforce FX5500 256MB bough for two months, it was find at first bu
after that, it have that pink screen problem, but the videocard and th
heatsink have no dust, it clean. so i try different video card, and th
out come that everything fine, but when i switch back to GForce card i
again, the pink screen came up again, sometime, it switch back to norma
screen for few minutes then it return to pinkscreen. i wonder if tha
cause by the videocard heatsink, not cool enough? can i change th
heatsink of that videocard? or what's wrong with that?

appreciate for repl

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cuoctinhtay3