What's Causing Appcrash and Bsod Events, General Instability?

SOLUTION: It was the RAM settings all along :-| It never occurred to me that the stock settings on a stock board with stock RAM would be so far off that it'd cause system instability. I've never done any overclocking, so I never looked very closely at those settings. Once I chose the DOCP profile that matched my RAM, everything cleared up, and it's even a little faster. Thanks to Twisty Impersonator for the process guide and to magicandre1981 for the suggestion that prompted me to check the settings. Hopefully, this will save someone else 2 years of frustration.

EDIT: Well, I think the cause has become clear. After replacing ALL the hardware, and STILL seeing a problem, I decided to go back to the hardware idea. In short: if I run with two sticks of RAM, everything is fine. It doesn't matter which two sticks. If I put in all four, I start having problems. This seems like a pretty clear indication of a bad motherboard.

The Symptoms:

For the last several years my machine has been generally unstable, off and on. Typically manifests as BSODs with varying stop codes.

• Upgrading the RAM improved the stability for a while.
• Upgrading the motherboard improved the stability for a while.
• Replacing the C: drive improved the stability for a while.
• Refreshing or reinstalling the OS has occasionally been necessary, and usually improves stability for a while.

I have replaced literally every functional component in the system, except the CPU and Blu-ray drive. I have not ruled out the CPU, but there is still a vast swath of software-"things" that might also be at fault.

Each time, the problem has returned after a few months.

Most recently, the symptoms have changed slightly. I am open to the possibility that this is a completely unrelated problem, but it seems too similar to the problems I have been battling the whole time, to be mere coincidence.

A few weeks I rebooted my computer to update, and it would not POST. I fussed with it for a while (checking connections, MemOK! button, disconnect power, TPU on/off, EPU on/off, etc.) and got it to POST, but the OS would not load. I forget the exact presentation of symptoms, but IIRC it would just sit and spin.

Reinstalled the OS and things were quiet for a week or so, until apps began crashing. At first, it seemed like all the apps that were crashing were installed on the same SSD. Without room to move things around and test, I upgraded to the new Samsung drives. But apps are still crashing.

• Flashed latest BIOS update. No change.
  • Turns out, you have to reset the CMOS when you flash the BIOS. Potential symptoms are much like mine. I reset the CMOS. No change.
• It was generally high-demand applications that would crash (Dishonored 2, Diablo III, ESO, etc). But crashes are happening between 35°C-45°C for CPU and GPU - So probably not temperature.
• It is not running out of RAM.
• MemTest has never shown any problems. I have run it dozens of times.
• No CPU test has ever shown any issues, except at high temperatures.
• No GPU test has ever shown any issues, except at high temperatures.
• I've reinstalled my video drivers a few dozen times.
• I had Task Manger crash while I was watching yesterday.
• Tried to install a Windows Store App. Some background process crashed. Had to try again. Worked fine.
• Event Viewer has just AppCrash events

AppCrash events are being produced by a wide range of applications. Varying sizes, locations, demands, etc. It is typically once a day, maybe less. But high-resource applications crash pretty reliably within 30 minutes or so.

I should clarify that these are not Windows is looking for a solution AppHang events. The application just vanishes, like I closed it, and Windows has nothing to say about it except the AppCrash event in the Event Viewer. Less often, there is a BSOD. Lately, I have seen IRQ not less than or equal, and others that I cannot remember... (I don't have any memory dumps anymore? That's weird...).

System specs:

• OS: Windows 10 Pro (upgraded from Win7 during free upgrade period)
• CPU: AMD Phenom II 1090 (no overclocking)
• Cooling: CoolerMaster 150mm CPU fans, several case fans
• Mainboard: ASUS M4A99X EVO R2.0
• RAM: G.Skill 16GB(4x4) DDR3-1333
• GPU: MSI GTX 970 (no overclocking)
• PSU: Corsair CX750M
• System drive: Samsung 850 EVO 500GB
• Other drives: Samsung 850 EVO 500GB, other conventional drives, optical drive
• A/V: Windows Defender, no other AV