BIOS Corruption:
While rare, it does happen from time to time, resulting in strange system behavior and instability.
1a - Yes, that is possible.
1b - No, that is not possible;
How To Clear CMOS (Reset BIOS)
1c - Yes, see my opening statement about BIOS corruption.
1d - Not likely, but hardware failure is possible from any number of things. Some are less likely than others.
PSU:
PSU failures are the most difficult to track down without a multimeter. They cause random problems on systems and usually point to other hardware as the cause of those problems.
2a - Yes. This is more likely if the PSU was already on its way out.
2b - It could have, but Windows does a pretty good job of avoiding these types of inconsistencies. 3rd party backup programs are more likely to cause issues with removed external drives.
2c - Your network device, your hard drive, and your RAM are used the most during downloads. The same for browsing, but your graphics card can also be involved during browsing. Your PSU is used for all system activities, so it is also a possibility.
2d - I don't believe in coincidences.
I doubt it is a coincidence.
Misc. Questions:
3a - Hard to say whether the graphics card would be involved in the crashes without more testing. It seems unlikely given the behavior you describe, though.
The shut down, removing power sources, and holding down the power button for 15-30 seconds are steps I recommend all the time. I would not recommend them if I thought there was any danger to your system.
Given the BIOS changes from those steps, I wonder if you do not have a bad CMOS battery that is the root of your issues... It may also be the motherboard itself that is faulty. I recommend contacting the manufacturer to find out if that setting change is normal given the steps you are doing.
Memtest86+:
Good news on Memtest86+, but you should run it again for 7-10 passes when you are able to.
Also, I would recommend running your system with only 8 GB in at a time and seeing if you have different behavior with downloads and through Windows. Remove two of your modules and see if the system is then stable. If so, replace those two modules with the remaining two modules and see if the system is still stable. If it is stable with all four modules running separately, it may just be that you need to change some BIOS settings for the RAM to work together.
The BIOS settings are typically designed with 4 GB in mind, and they will usually work with up to 8 GB installed. Anything over that, and the system will often require some BIOS setting tweaks.
As you add and remove hardware, follow these steps for ESD safety:
- Shut down and turn off your computer.
- Unplug all power supplies to the computer (AC Power then battery for laptops, AC power for desktops)
- Hold down the power button for 30 seconds to close the circuit and ensure all power drains from components.
- Make sure you are grounded by using proper grounding techniques, i.e. work on an anti-static workbench, anti-static desk, or an anti-static pad. Hold something metallic while touching it to the anti-static surface, or use an anti-static wristband to attach to the anti-static material while working. If you do not have an anti-static workbench, desk, or pad, you can use your computer tower/case by finding a metal hold in it, such as a drive bay.
Once these steps have been followed, it is safe to remove and replace components within your computer.
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