Bunches of dots on the screen is a common symptom of damaged video RAM. If the dots show up in screen shots then the video RAM may be your problem.You could try underclocking your video RAM with ATITool (instructions here). If reducing the video RAM clock rate makes the dots disappear then it usually means that the video RAM is damaged or overheating. Reducing the clock rate doesn't always "fix" bad video RAM but it's pretty common. If it really is bad RAM then there's nothing you can do about it other than live with a reduced clock rate or cool the RAM better. ATITool has an artifact tester built into it which you can use to see if lowering the clock rates solves your problem.