So there you are, minding your own business.
You try to restart your Windows 10 puter, and you end up with the new Sad Face Blue Screen of Death!
At the bottom of the screen, you see:
Stop Code: 0xc000021a
No matter what you do (like the automatic Startup Repair), you appear to be sunk… Windows just won’t boot up anymore.
What to do?
Many of you have installed Windows 10 on your puters only to discover that every time you boot up, you get a screen that reads: Choose an operating system
Windows 10 will of course be at the top of the list, usually followed by either Windows 7 or Windows 8.1. If you pick Windows 10, it fires up and everything works normally.
Obviously, there is still something wrong: Why is Windows 10 asking if you want to boot your old version of Windows? After all, you upgraded, right?
Fear not! There’s a very easy trick to remove this boot menu – and it works for all flavors and versions of Windows all the way back to Vista at least…
You know the drill: You get a new motherboard. You upgrade. And then the fun begins!
Sometimes, one device or another in your system is not detected properly. Other times, you can’t boot into Windows.
You may even find that you can’t even get into the BIOS after the initial setup… Instead, you are met with a blank screen with a blinking white cursor, and pressing Del or F2 does nothing!
In some cases, these problems can indicate a defective motherboard or other component. But before you go RMA-ing anything, try changing the following settings in your UEFI BIOS…