Stuttering sound/video, won't go away until restart.

So, I bought my XPS 17 around october 2012. It's been great for a couple of months, then it started doing this really weird thing.

It started as just random cracking noises, along with mini-video stutters, as if it blocked for a part of the second.
Then with time it got worse, my whole machine started going in 'slow-motion' mode, making everything work slower, and with a horrible robotic sound effect. That thing got fixed only by restarting. And since shutting it down would take like 5-10 minutes, I just held the power key until it turned off.

After that happened, on boot I used to get various blue screens, most often with "Memory dump" on the bottom.

Since then, I gave my laptop for repair in two different places, it passed 2 or 3 BIOS tests with no problems, but when the guys tried to reinstall it, they faced numerous blue screens too. They've told me numerous times that they find these problems really weird and don't know why they happened, they just got assumptions (and yes, it's an official service). So they tried to replace this, tried to replace that, bottom line from the repairs: changed motherboard, processor, fixed some software hard-drive problem and reinstalled windows.

I got my laptop back yesterday, everything was cool, until I tried to install a program (3ds max 2014 if that helps) and then that stuttering thing happened again mid-instalation.
Then today I ran a 30 minute 1080p video on youtube and on 15th minute it happened again.
I have videos of it, I might post the links here, if that will help with something. 

Funny thing is it doesn't even happen the same way in different situations. In FIFA it started slowly and over 1 minute, while watching videos - it's almost instant, while playing League of Legends .. it does not go in slow-mo mode, but after I quit the game the whole machine starts working slower, as it's loaded with work to do. 

I've read countless topics, did so much stuff, checked drivers, changed settings here and there - nothing helps.
Even a 5 week maintenance didn't help.
Help.