Impossible GPU Problem [?]

Hi there folks! So a guy told me this is the best hardware forum nowadays, so i decided to share my stuff with you all, since i've been trying for more than a year now, and it's pissing me off.

I have a problem you see, and as far as i know, its a Graphics Processor problem. So, first thing, this is my computer configuration:

Computer: Dell L502X (Notebook)
Processor: Core i7 2630QM @ 2.00 Ghz
GPU: GeForce GT 540M
OS: Windows 7 Ultimate Edition 64bit.
Motherboard: Dell Inc. 0NTJ03
Display: 1080p Full-HD (1920x1080)

So... let's begin my story:

This computer is almost 3 year-old now, but i got for 2 years. 18 months ago i started gaming on it, heavy stuff that consumes big amount of GPU and CPU. First i played games like Crysis, Mass Effect 2 and 3, and others. All of them runned perfectly at the time.

Then, something happenned, one day my computer started to overheat. Yes, seems like the problem was right there and already detected, except for the fact i never found out why it was frying.

So, i started to look around for solutions. I Googled, a lot. And i did everything i supposed to do. First i used HWMonitor and CPU-Z to monitor my stuff, found my components (GPU and CPU) were almost in hell, like, when i was gaming they reached almost 100°C, and that was bad, really bad. I got lots of buzzing-freeze sounds, BSOD's, crash to Desktops and all sort of error you can get. Things were bad.

I changed the thermal compound on both processor and GPU, twice. Dusted my fan, and everything else inside my computer. But still i was getting error after error. After installing CPU-Z i found out my computer was overclocking, my 2.00 GHz CPU was going to 2.80 GHz, which is pretty much its maximum levels. I fixed that too.

But no matter what solution i tried, it never worked. I run MemTest86, rolled my nVIDIA Drivers back and installed each version avaible, tried to format my computer (3 times), tried to manage nVIDIA PowerMizer, bought an external fan. Played my games on minimum settings with low resolutions.

I never really managed to get this fixed. You see, even games that demand low-specs used to bug with me. Like League of Legends, whose requirements i clearly have, don't run for more than 10, 15 minutes. However, other games that demand more, like Saints Row The Third, run perfectly well and never crash.

So this got me into confusion. My computer run some games, but doesn't run others. For exemple, my computer runs Skyrim with all add-ons on a low-resolution, but never crashes. However, it crashes for example when i play Age of Empires II, which is kinda old already.

Lately i have had this problem, where i'm trying to play Saints Row 4, but after minutes my game crashes, in a lot of ways actually. From playing this game in the last 3 days i already got a couple BSOD's, lots of crash to Desktop, some freeze-buzzing crashes and that good old message "NVIDIA Windows Kernel Mode Driver, Version 331.82 has stopped working and successfully recovered." I tried to run the game on the lowest specs, with a low resolution. But... well... it crashes.

By the way, my drivers and BIOS are all up to date. I tried every solution i've come across to. Even changing sound configurations like frequency and all that... none of them worked. So i'm now sharing my problem with you guys.

Think anyone can lend me a hand and give me the final solution that will allow me to be happy? Feel free to ask me anything that might help. I'm counting on you guys... or else i'll have to throw this notebook on a pit, salt and burn it.

Also, english is not my main language so... sorry for any mistakes.