HELP: M6500 Lag spike/Cracking sound

Hello, I have been with my M6500 for about 1.5 years, and didn't have a problem until 2 months ago. Since then I and the Dell Support Team have been trying to find a solution, but the problem is still there.

M6500 specs:
Windows 7 Pro 64bit
Intel Core i7 X920
16GB RAM 1333mhz DDR3
1GB ATI FirePro M7740
128GB SSD Samsung (main drive)
500GB Hitachi 7200RPM (second drive)
Mini WLAN 1397 Dell
Gigabit Ethernet Broadcom NetXtreme

Aftermarket parts (1 year old):
4GB RAM Samsung
500GB Hitachi 7200RPM

New parts (1 month old):
128GB SSD Samsung
12GB RAM Corsair (4x4x4)
Motherboard

So far from Dell Support they have replaced, first the Motherboard, then the SSD, with no results. From my part so far, I have formated my M6500 about 6 or 7 times, try different BIOS, upgraded every driver and software, installed system maintenance software (ioio System Mechanic) to free the registry and other tweaks. Even try several fix found in this an other forums, such as switch from ACPI to MPS, or the Crackle Sound Fix for the WLAN from dell. And still no fix.

The problem itself is just a lag spike with a crackling sound, giving me slow FPS or even a short freeze and if Im hearing music or any sound, then sound crackles. This problem occurs more often when using the internet, such as playing online, watching youtube or listeting iTunes while running other programs.

The problem is more like a confort issue because it doesn't give me any blue screens or errors, is just a few seconds of annoying sound. And it is not annyoing if you aren't listing music, watching videos or playing, because you can't notice it at all.

But the problem is getting to my nerves when I'm playing WoW, watching movies or listening music!

Right now me and the Dell Support are running out of options, and it's a great laptop. So that's why I came here if anyone have to say anything about it, maybe we are missing something or someone had a problem like this also.

Thank You.