My screen shows lots of coloured lines especially I play games and sometimes during start up. Is it because of heat? Can someone help me with the problem?
In addition to what iss said, you should open your case, clean out any dust and check to see if the fan on your graphics card is working properly. There might be some dust accumulation on that fan as well.
I had the same card and it did the same thing. I returned 2 and this last one still did it occassionally. It would only do it at startup though and turning off the computer and then turning it on cleared it up. Never has an issue with gaming. Those cards are insanely hot. Mine would get so hot it would overheat the motherboard and cause it to lock up. A VGA Silencer cleared up the heat problem.
I have a All in wonder 9800 pro and it was (1) insanely hot, and (2) the fan was ****. It fell off. So i screwed a 70mm fan i had lying around (yes 70mm) into the fins on the heatsink. The card now runs at 29*C. Thats because the fan in particular is like 4500rpm and around 50 cfm yet somehow it is still pretty quiet.