Acer 5920g graphics problem

Hello and sorry for my english is not my mother language. I have an acer 5920g. When i turn it on one day the screen was all vertical lines and the half screen became white and the other half pink and i couldnt see anything. It did it from the beggining before even show the bios diagnostic. After a lot of tries and after i connected with external monitor i managed to fix it and the laptop booted normal with no problem (with and without the external monitor). I did a couple of restarts to make sure its ok but after 2-3 restarts i show in the screen some hotizontical green lines in some parts of the screen and it get only in the loading vista bar. After a restart it shows again vertical lines in all screen and it doesnt seems i can fix it this time. Has anyone any idea what causes it and how can i fix it? Also i have the same laptop (5920g) with same characteristics but seems motherboard is not working and i wonder if the problem is in graphics card if i can change it from the other laptop i have. Is there possible to change the card in 5920g laptop??? thanks a lot.
 
The graphics chip on the motherboard could be damaged by heat. It also may be that the video cable from the LCD panel to the motherboard is damaged
 
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