Hey guys, I ran into this problem only recently. A few weeks ago, I was using my computer, its a 3 year old XPS M1330 model. All of a sudden, while I was watching a video on youtube, the screen on the video got grainy with multicolored little dots. Its almost as if the pixels stopped working and became neon green. Then, the whole video froze up, and my screen became black with rainbow squares flashing all over the place. I then shut down my computer. A few weeks later, this problem became a lot more severe, and my computer wouldn't even show the startup screen with the dell logo or anything after that. I would turn on my computer and would be given a blank white screen that would eventually get faded vertical lines across it that you could see if you tilt the screen back. The pure white color would also become grainy with faint black pixels. Today, I turned on my computer and this white screen was gone, but the rainbow squares and multicolored pixels still showed up and caused my computer to freeze up. This problem has been reoccurring ever since, and its now pretty much impossible to use my computer for more than 5-10 minutes. I think it might be something to do with the video card, as my display doesn't have any damaged pixels and has never needed a repair. My motherboard crashed last year, so maybe it has something to do with that. If you guys have any ideas, go ahead, cause I have no idea what this might be. I couldn't even find it with google.
The video chip has failed - you will need a replacement system board. If you plan on keeping the system a while, get the Intel video board - not another nVIdia board, which will simply fail again. You'll need a new heatsink to switch from nVidia to Intel.