YAY!!! I finally FUCKING FIXED IT!
So, in case any of you might have this problem in the future, here goes the cause of the problem: Today, like any other day for the past 2 months, I turned on my PC and quickly fired up PES as soon as the Windows Desktop showed up (while I was connected to the Internet). Usually I surf the net a little bit, or take some time doing different stuff before I run a game. But today I wanted to see if the problem had "magically" gone away, same way it "magically" came up by itself overnight. Of course... the problem was still there.
But, to my surprise, right before I started the match, PES got minimized by the typical error screen that Windows 7 shows up when a program/process fails, and the program/process failing was
"bmufa-64.exe". So I did a quick google search, because I had never heard of that EXE before. And, to my surprise there wasn't much information about it, but some people were reporting that it made their videos play jumpy and slowed down their computer. They said that it had something to do with RealTek Software, and it could be found here: C:\users\NAME\AppData\Roaming\Realtek Semiconductor\Realtek HD Audio Manager\1.0.0.653\RAVCpl64.exe So I deleted that file
And I also did a search for the "bmufa-64.exe" itself, I found it under some kind of Windows Prefetch folder and deleted that as well.
Also worth mentioning, I found out on this website
http://www.isthisfilesafe.com/sha1/30C9421DE9649F03641D89D01DA3D17481D3228C_details.aspx that the company under BitCoin is UfaSoft, so I searched my computer for "Ufasoft" I found a folder into the Roaming folder of User/Appdata of my HDD, and deleted that Ufasoft folder.
Finally, I used CCleaner to clean the Registry, and then rebooted my PC. Now the problem is finally gone and I can play games without sutter again.
The coinminer will use your CPU processing power to generate the coin, some infected user may felt their PC lagging due to this culprit. I guess it will send those generated "bit coin" to the culprit/creator via unknown connection, since it is "usable" digital currency like facebook credit.
That's why the problem only happened when Internet was available... cuz that's when the BitCoin Miner started to send information. It was unnoticeable if you weren't running a game, because the PC memory was pretty much free. But when some heavy application (such as a game) started to consume memory, that's when it becomes noticeable.
And I'm thinking that the whole trick to get to figure out that BitCoin Mining crap was possible thanks to running PES as soon as Windows started. Seems like that "bmufa-64.exe" process/program didn't have enough time to load properly and when PES started it made Windows give me that usual program error message which, otherwise, wouldn't have shown up.
BTW I'd suggest you all follow the steps I described, since Anti-Spywares and Anti-Virus softwares won't detect that BitCoin Miner.