Alienware M17R3

I bought my Alienware 2y years ago. The laptop turn to black screen then restart. It was just 1 or 2 times per week at first, then the problem became more and more seriously, it restart 2-3 times per day, and it's randomly, sometimes happened between I play games, some times happened when I use browser. I called Dell and they send a technician replaced the video card. The problem seems been fixed, but my laptop started turn to black screen again 2 month ago. So I called Dell again on November 9. After a short diagnosis, they think it's the video card's problem. So they sent a technician to replace the video card. After the replacement, there is a lot dots on the screen, I can't even read what's on the screen.The technician think it's the problem because the video card was damaged during the shipping, so he called dell and ordered another video card, after he replaced the second video card, there is the same problem happened again.  The technician think it's the problem of motherboard, so he ordered a new motherboard and ram. The same problem happened again this time, so he called Dell and Dell told me sent them my laptop, they told me they gonna fix it in 3-5 business days, I have send it on Nov 21, and I haven't get it back until now. It takes almost 1 month to fix a black screen problem. It's close to the end of year now, I got lots of works to do, but I still can't get my laptop.

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