I have a Dell D820 (recently upgraded to 4 GB shared RAM) that started giving me the dreaded "Matrix" and fuzzed-out display (Vista). On examination, it seemed that shaking the screen caused an effect on the display (ah ha - hardware). Plugging in an external LCD showed the same problem (ah ah - not the laptop screen itself). During the day the problem got worse to the point that I have no display at all. Assuming that the inverter only controls the laptop screen, it must be the GPU, right? Strangely, the laptop seemed to last longer in Windows Safe Mode (VGA) than in true WUXGA. Could the cheapo 4 GB eBay memory (shared with the GPU) have anything to do with this (I swapped and removed the cards with no difference)? I'm on a business trip with three deadlines on Thursday, so any help or suggestions would be most appreciated.
Being that the system exhibits this in Windows, in SafeMode, and on an external monitor it sounds like a hardware problem with the graphics card. If the original ram did not correct the problem you will need to contact Dell if you are under warranty to have the motherboard replaced. Even though the video card is discrete it is integrated on the motherboard.
If the system no longer has warranty you will need to buy a replacement motherboard and have it replaced. On this system there will be a few different choices for a motherboard because it was sold with both a 128mb and a 256mb graphics card as an option.
Here is a link to the service manual for your system http://support.dell.com/support/edocs/systems/latd820/en/sm/index.htm
To receive further information about this system please visit http://support.dell.com/
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