Windows 7: PC freezes for ~20sec & restarts, noticed while browsing firefox

Memtest is another over night test . If you see any red lines on the bottom . Stop the test and test each ram one at a time on every DIMM slot . If you're using Dual Channel memory and still under warranty with the memory manufacture . RMA both of the sticks even if one of them turns out good . If your warranty expired on the memory sticks purchase a new Dual Channel Kit .

Well, after running the Prime95 overnight = no errors (OK).
I also ran from this morning till now (~8.5 hrs and 9 passes) memtest86+ v.4.2, again without errors (OK).
The Furmark gave me a constant temp of about 99-100C (leveled out) after around 3-5 minutes without any artifacts (OK).
My only thought right now is that maybe the HDD is the cause of all these crashes !? (because the seatools software found several bad blocks on the system partition and repaired them).

Try this Seagate for Dos

SeaTools for DOS | Seagate

How to burn an .iso image onto a CD

I will run this test again, although I already ran in a week ago.
After it fixed the errors it found, I ran another pass to verify everything is ok and it did turn out to be OK.
The only thing that can be bad in here is the mobo itself, but I can't really test it or replace it for the sake of a test...
So I don't really know what's the reason for these BSODs.

Well, Ran the Seatools DOS - Long Test.. Checked out OK.
Now what?? This is frustrating!

Try updating your BIOS from 2208 to 2209 then run Prime95 again.

Well, new BIOS updated, Prime95 checked OK.

Keep this thread opened if you get anymore blue screens upload the dmp file .

OK,
Installed new Samsung SSD and reinstalled windows (this time the right/legit PRO version.. :) )
For the time being, while using both the new SSD and the old faulty HDD, I encountered only one crash with the same characteristics (BSOD 124).
I disabled the old SYSTEM partition and left only the other two DATA partitions and my system is stable for now. I'll update this thread again after running this setup for a while.

Well, after couple of days I had the same "restart" with the BSOD 124.
Now I can no longer blame the HDD as it was disconnected.
so.. If indeed my:
CPU passed the Prime95 test
RAM passed the MemTest
GPU passed the Furmark test
New SSD with a new Legit copy of Win 7 Pro with all updates installed
.... Does it say I have a MOBO malfunction and should buy a new PC ??