Please help with N81Vp, voltage spike

Hello fellow members,

I need help trying to fix my N81Vp.
Yea, it's pretty old, purchased from GentechPC around 2.5-3 years ago.
It's recently been having over-voltage problems.

I think it's voltage problems because around a year back when my charger was dying/faulty, it did the same thing.
Back then, whenever I loaded something graphic heavy, it would turn the screen black with the backlight on, turn up the fan, then distort the sound like you're hearing robotic bits, and freeze that way.
I realized that playing on battery mode fixed my problem thus I changed my charger and it worked.

Problem is, around a month ago, it started to do the same thing.
Whenever I'd alt-tab too fast, play games,try zooming in on a photo, watch a video full-screen, it would occasionally do the problem listed above: "turn the screen black with the backlight on, turn up the fan, then distort the sound like you're hearing robotic bits, and freeze that way."

However, this time it wasn't the problem of the charger.
I tried playing on battery mode and still the same issue arises.
I've restored my computer, same issue.
Flashed my bios (which doesn't give me control of my gpu) with the latest, same issue.

I also checked my temperatures and gpu%, and it'd still happen when under 40C/ 10% usage when I'd alt tab too much or something.

It then occurred to me that I should try undervolting my computer via third-party software.
This solution WORKED but maybe only 75% of the time. AtiTools would make shockwave flash not work (I don't know why) and MSI Afterburner too doesn't work all the time. I did unlock everything on MSI but since I cannot have control on my voltage (motherboard incompatible I guess), it doesn't work =(

Is there a way to change my registry settings or use external software/bios to regulate and strict my voltage?

Thanks for reading :O