Clouds of pink dots are infesting my screen.

Hello,

I bought a VAIO VGN-FZ21S laptop about 7 or 8 months ago. I was very happy with it until about two months ago when I encountered a problem where my laptop would no longer start. I then sent it for repair and received it a few days later with a new motherboard. So far, nothing too serious as the after-sales service is indeed excellent.

However, about two weeks later, I encountered another problem. I thought it was the screen because this issue did not disappear after restoring the system and then doing a complete reformat of the computer. So I sent it back once more. This time it took a little longer, and when they returned it to me, it came with the note 'unrepaired.' Apparently, my computer had nothing wrong with it; they hadn't done anything, and yet the problem had disappeared. Everything worked perfectly until now, but for the past week, the problem has returned. Well, I'm doing an antivirus scan with Avast, looking for malware with Ad-Aware and Spybot, nothing. The VAIO hardware diagnostic finds nothing. I have once again reformatted everything to return to the original configuration, but it doesn’t change anything; the problem is still there.

I hope someone can help me because I am really frustrated. I don't know what to do. I need this laptop for my studies, and I don't have any other computers; it's the only one I have. So I really don't want to send it back to the after-sales service again, especially if it’s once more for them to tell me that there is nothing wrong and that the problem starts again two months later.

Well, I will try to describe my problem, but I emphasize that I am not really a specialist.
My screen is covered with clouds of tiny pink dots that look like clouds. The problem is not permanent. Sometimes it is not present at all, and when it is (meaning most of the time), the intensity of the problem varies greatly. One detail that may be important (I don’t know) is that I took screenshots to show what it looks like, but when I looked at them when the problem was not present, I realized that my screenshots were normal; they do not show the problem. These clouds appear right from start-up, even before Windows starts, the VAIO logo is affected by this problem, but it's discreet because these dots do not appear on a white or black background. These tiny dots flicker very quickly (from a distance, they seem fixed, up close you can see they are actually flickering) in place on the still images, but they are different from one image to another. In videos, the clouds of dots are in constant motion. I don’t know if this is helpful, but the problem is also present in safe mode.
On some images or videos, the pink dots are accompanied by small clouds of turquoise dots that are much more discreet. These pink dots are present most of the time, but they can appear or disappear, depending. One last thing, the dots are also present during reinstallation after formatting.
I don’t know what to do anymore. I hope someone can help me. I thank that person in advance.

I took pictures of my screen to give you a little idea. I don't know if I can post them. I will try.

My configuration:
VAIO VGN-FZ21S
Intel Core 2 Duo T7500 2.20 GHz
2 GB DDR2
NVIDIA Geforce 8600M GS
Windows Vista Home Premium

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