Electrical sizzle sound coming from PC case

AMD Phenom II X6 1050T 50 °C

8,00GB Dual-Channel DDR3 @ 618MHz (9-9-9-24)

ASUSTeK Computer INC. M4A88TD-V EVO/USB3 (AM3) 44 °C

ASUS MS238 Monitor (1920x1080@60Hz)

1024MB ATI AMD Radeon HD 6800 Series (ASUStek Computer Inc) 70 °C (Speccy program gave that temperature info, I alt-tabbed a game right now I'm not sure if that's idle level or my GPU is getting rekt or wrong info, I'm afraid of I applied not-enough thermal paste)

465GB Seagate ST3500418AS ATA Device (SATA ) 37 °C
232GB SAMSUNG HD250HJ ATA Device (SATA ) 36 °C
232GB Western Digital WDC WD2500AAJS-00VTA0 ATA Device (SATA ) 39 °C

That acting like a Decepticon problem has started 2 weeks ago, fresh start for PC yesterday, problem is still there. How can I disable PCI GPU and use internal graphics?

News from problem:

1. It seems that electrical sizzle sound is coming from PSU.
2. PC has started to give random shut downs, and following "Asus Anti-Power Surge" error at startup in a blackscreen.
3. PC startup screen is telling random things like "Overclocking Failed", "Current CPU can't use Core Unlocker" after Anti-Power Surge error.

What should I do now? Is my PSU or CPU dying?

It is Coolermaster RS-620-ASAA-A1. And I do wonder what is Anti Power-Surge and why is it happening randomly. Yesterday I had hours of gaming without a problem but then I turned off my PC and came back; PC gave this error again and didn't start again, I am editing BIOS everytime almost every start and also it always turns off ASUS Core Unlocker by itself.

Should I just disable Anti-Power Surge protection in BIOS settings? Or is that a bad idea.

Hi again, I've managed to test the PC while case side covers are open to get a clear sense. I am hearing and I'm 90% sure that electrical sizzle sound comes right from there which PSU exhaust is here (same xClio case): https://imgur.com/a/RhbqVVC.

and currently I'm on internal motherboard graphics card as well (unplugged the external), which means I am testing if problem is from external GPU EAH6850. Result is interesting: electrical sizzle sound is still there but it lost kinda 70% of loudness of it (as I said above sound comes from PSU and it was really loud before).

I've continued to test with internal graphics. I've uninstalled all EAH6850 drivers and installed internal HD4250 ones.

Right after writing these above, I wanted to test internal graphics on Skyrim game: PC shuted down - reseted immediately when I started the game (didn't even see main-menu). It was again that same ASUS Anti-surge error screen at the start-up of PC. I picked "Load default BIOS setting and continue setting" (otherwise sometimes PC can't even get into Windows and stuck on Anti-surge every restart). Then I started Skyrim again, this time PC didn't shut down and managed to get into main menu screen but it was too damn laggy (idk if HD4250 is that bad) and had to close game. Then I've started TES:Legends which is not 3D heavy at all, this game main-menu was also 20FPS (a card shouldn't be that bad, maybe I used same HDMI cable as from EAH6850 and HDMI is heavy for it?). Remember these are all with internal graphics.
Anyway problems are still there without external GPU, sound is there but less, Anti-surge happened on a really bad way.

I also should mention I got Blue-screen two times right before Windows startup screen this week after managing BIOS to make it organized (because motherboard always does some weird OC by built-in OC Utility) (I know what I am doing in BIOS, I don't do anything different).

So what does that mean actually, I really need help. PSU dying? GPU unstable? GPU dying? Bottleneck? PSU power isn't enough? PC case assembly messed? This PC was working really very fine for 1 years with exactly same setup. While waiting for getting help from you guys I will do a fresh Windows install with re-enabling external GPU.