What if i only overclock the fan speed

is that will be useful to overclock only my video card fan speed to be more efficient maybe !! i don't know i got some heat problem with my 9600 gt video card and recently i saw a light horizontal purple lines across my screen flashing for seconds and vanished while playing a video game (skyrim) i did a tab-Alt to see the temp for my GBU i found it 75c i know it's not much but what reason could cause these lines ?
and by the way when i minimized the screen i found these lines still appearing on the desktop !!! any suggestion thanks for reading

Overclock fan speed?? The fan doesn't have any clocks, so that's impossible.

You can turn your fan speed up if you are having problems with heat, but 75c isn't a problem.

@geekapproved yes exactly that's what i thought that 75c is not an issue but why this lines i dont know and if my GPU is dead how could i be able to play for more than 5 hours without any freezing or a problem i saw these lines very rare and they are not that much u need to concentrate for seconds to see them !!! so what the hell is that

no i hadn't and my GPU about 2 years old and the core heat is 75c i think this not overheated why do u think the reason is GPU is there anything else could be the possible reason for that

Hmmm, I would have expected Furmark to reveal a problem. My reason for suspecting the GPU is that strange artifacts, lines, etc. appearing on the screen are normally indicative of a GPU problem.

Strange lines is definitely not good. Taking a step back, have you checked that all your drivers are up to date. If possible, a picture of these lines would help. If its not the GPU, that leaves the screen. Any information on that?

I have the same issue, i have a nvidia GTX 460, its about 2 years old and has workedwith no problems till i set it up with my i7 in the new system. I have had a few discolored objects during gameplay and also i get purple or green line across some videos when streeming from the web, and somtimes on my desktop. I am curious if this has something to do with a defctive intel graphics chip or driver compatability between intel and Nvidia. Have you found anything out?