BSOD about twice a day. Feels like I've tried everything.

So I did pretty much everything you listed, except for the BIOS/CMOS, and nothing was found. Yet I got 2 or 3 more bluescreens. Tired of all these problems I did a new clean install of Windows 7 on a diffrent Harddrive. Installed all the drivers (atleast I think so) and even changed the sata-cable between the harddrive and the motherboard. Yet only 2 hours later another BSOD came up.
It feels more and more like it would be a hardware error. Perhaps the motherboard?'
Should I remove the memory sticks that I added some time ago even though neither Memtest or Windows own memorytester found any problem?

The memory diagnostics are not foolproof. Further reading: Finicky RAM.

I would suggest testing your RAM by running Windows instead of a memory diagnostic tool. You may swap out your current modules for your old ones, or you can test the current ones individually. It's up to you.

• Before doing any RAM swapping, please download and install CPU-Z and Upload screenshots of the CPU, Mainboard, Memory, and SPD tabs. In the SPD tab, upload an image of each slot.
  
  Also, go into your BIOS and post all Voltages (CPU, RAM, NB, IMC, etc.) and all RAM settings (timings, frequency, etc.)
  
  Thanks to Dave76 for help learning RAM Stability
  
  
• Test the memory slots as follows.
  
  1. Shut down and turn off your computer.
  2. Unplug all power sources to the tower (unplug the power from the outlet/surge protector or PSU).
  3. Hold down the power button for 30 seconds (for your safety and the safety of the components) to close the circuit and drain all power from components.
  4. Remove the casing.
  5. Remove all but one memory module making sure you are grounded while doing so.
  6. Replace the casing and put the remaining memory modules in a safe, static free environment.
  7. If the problem persists, repeat steps 1-4 and move the memory module to another slot (while staying grounded, of course).
  
  
  Do this until all slots have been tested. If all slots fail, the memory module may be bad. Test with one of the remaining modules. Continue one module at a time in one slot at a time until you find a good module and good slot. Test remaining modules in the good slot, test good modules in other slots to find bad slots, etc.
  
  
  Test by doing your normal routine in Windows for twice as long as it takes to get a crash or until you get a crash, whichever comes first. You can also test by doing the tasks that generally cause crashes.

So I was resetting the CMOS/BIOS to make sure that I wasnt overclocking anything. After doing this my computer is kinda not working. When trying to start it goes to the "swilry" windows thingy during the bootup and then I think it bluescreens. It flashes a bluescreen and some text for about half a second before the computer reboots. After the reboot windows wants to try and repair. However it doesnt find anything and even when trying to reinstall windows it eventually goes back into bluescreening during bootup.
I guess there were some settings I shouldnt have messed with. ATM looking around for solutions for this problem.
Any ideas?

Nevermind. I managed to fix the bios problem. Will see how it goes from here.

Alright, glad you got back to Windows. Nice work! May I ask, how you fixed it?

It was some setting concerning AHCI.
I do think you are correct that it might be faulty RAM that is the culprit. I was trying to install/download Guild Wars 2 and it crashed a couple of times complaining about "Corrupt memory" or something of that sort. I'll remove some of them and see how it goes.

AHCI makes sense. Sometimes the BIOS reset changes AHCI settings, and they have to be reset manually by the user to be able to boot. I'll keep that in mind as a possible step when I let people know to clear the CMOS.

Your troubleshooting sounds like good steps. Let us know how it turns out.

Been about a week now without any bsod or games crashing. Its not conclusive but it feels like it was faulty memory that was the problem. I guess memtest cant find everything. I will probobly look into buying some new sticks since I notice quite the difference with 4 instead of 12 GB.


Thank you for the help and I hope I wont be needing it again

You're welcome. :)

Just make sure when you get any new RAM that you get the kits at the same time, same models, and same voltages. It is best not to mix and match any RAM or you may end up with instability again.

You are better off getting RAM that runs at 1.5 V instead of 1.65 V for an i5 processor, as well.