Early Intel Imac, Hardware or Software failrue?

i have 1 of white duel core imacs has started acting on me.

when boots up, can tell there pixel errors, , few small video artifacts on screen seems me indicate video card. can log machine, running programs pretty hit or miss, in can launch safari, , freezes up, or crashes. after few minutes, mouse still responds, finder seems freeze up.

given fact there video errors, , suspect video card/logic board may failing. have dealt thermal issues in past machine, , have managed clear them cleaning out fans, , adjusting fan speed up, time not seem working have never had not run programs before. worth trying reinstall osx, , see if clears up, or should consider hardware error, , ready move on?
thanks,
alan

 

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