BSOD mostly when playing games, DRIVER_IRQL_... and PAGE_FAULT_...

I'm running memtest v4.20 atm, and currently it's at 4 passes without any errors.
I'm gonna leave it on at night to see what happens.

So I let memtest v4.20 run all night long, and I got 3 errors:
- pass 10 test 8 - 9246.9MB - Err-Bits 80000000
- pass 11 test 5 - 9246.9MB - Err-Bits 80000000
- pass 11 test 5 - 9310.9MB - Err-Bits 80000000

How can it give errors at RAM over 9000MB? I only got 8191MB? Besides that, what do to next?

Edit: just got another one, after pass 9 suddenly the errors pop up lol.
- pass 11 test 6 - 9246.9MB - Err-Bits 80000000

Test one stick at a time.

I've just tested one, and I didn't had any errors, I'll test the other stick tomorrow.

Another thing, I just checked my RAM sticks again, and I thought they were exactly the same, but one is 1.5v and the other one is 1.6v, could this give any problems?

Yes it certainly could, since that means they are not matched running different specs.

I've tested the other stick, it's currently at pass 8 and still no errors...

Both sticks separately don't give any errors, and together they only give errors after more than 10 hours testing, but outside memtest I get a BSOD around every 1-4 hours...

Could this problem be caused by the fact that the voltages of the ram sticks don't match? Could the problem be caused by another defect hardware, like the CPU or GPU? Could the problem be that I didn't set the right voltages in BIOS?

More likely the unmatched sticks are negotiating a compromise setting in order to boot, but neither are completely stable with it.

I would try a matched set of ram.