I have a Dell 8700 XPS running Windows 8.1 Pro. I have a Dell support tool on the that machine that updated drivers etc. I noticed on Sunday that an update was installed by this tool. Since then (ie from the very next reboot after that update) my system crashes with a c000021a error, not long after logging in (within 5 minutes). It doesn't give me enough time to go into the Dell support tools to see what that update was. I did note that a series of Windows 10 Windows Updates had failed, so I figured it may be in some sort of hallway-house with regard to Windows 10. The machine is stable in safe/diagnostic mode. Usually running Windows Update is a good idea in these situations, so I did and it in fact load Windows 10. Again, stable in safe mode but with normal boot it still gives an error (albeit renamed to "critical Process Died).
I had only rebuilt this machine 3 months ago and it was fine. Regrettably there are no restore points saved.
Any assistance would be greatly appreciated.