0xc0000020 error on start (DLL error) with all ArcGIS products on Windows 10.

[RosemaryAlles]

This question has been asked several times, without a satisfactory response regarding a solution, I am asking again, in the hope that *someone* has a solution: (other than reinstalling Windows) 

 I am running ArcGIS 10.5.1 on Windows 10. And have not had any problems for years except this one, which started 2 days ago; since then, I have repaired, uninstalled, reinstalled to no avail. ArcGIS runs happily for a while and when closed it is always questionable if it can be opened again without a problem; generally it WILL open, however, I can almost guarantee that if I power down the computer and restart it - ArcGIS will fail with this error message - see below: (several pop ups related to different DLLs, all of whose sizes appears to have shrunk to zero). 

++++++++++++++++++++++++
Error message:

"C:\Program Files (x86)\ArcGIS\Desktop 10.5\bin\AppInitializerLib.dll is either not designed to run on Windows or it contains an error try reinstalling the program ... Error status: Oxc0000020"
++++++++++++++++++++++++

The only change to the computer are the auto updates by windows, I have a suspicion that updates may be causing a problem? I am not sure. Weirdly this seem to happen (although I am not 100% sure) during the window of time that the computer is designated not to be active, and ergo, updates are possible. I have run a malware checker, virus checker and file system checker, all which tell me that the system is ok; the problem appears *only* affect ArcGIS so far...

[RogerBarnaby]

Possible solution. I had downloaded python to use independent of ArcGIS.

It was in a folder C:\ProgramData\Microsoft\Windows\Start Menu\Programs\Python 2.7

I uninstalled this program and deleted the folder.

I then reinstalled ArcGIS Pro and it seems to be working.

Does this make sense?

I will let you know if this solution does not work out.

[RogerBarnaby]

Nope, sorry, only works until I restart computer

[DaveBarrett]

I encountered this error on a windows 10 home machine that had recently updated to the latest fall creators update version 1709.

Only solution was to reinstall pro. 

With regards reinstalling windows 10 there is the option to refresh, reset or restore you can also build recovery media from windows. Download it here.

This is the first time I've run into this error so I'll keep an eye on it and see it reoccurs

[BrookeWilliams1]

I solved this problem by going into settings in windows 10, going to app, clicking on the ArcMap 10.5 icon, clicked uninstall, then in the installation window that pops up I selected the repair option, then followed the install prompts. After this process software worked again without having to register the software or anything like that. Previously I had no problem using ArcMap on Windows 10, it just stopped working and came up with this error one day. 

[DanPatterson_Retired]

once you have it working... and just for a test... also go and create a 'restore point' .  This can be created via regedit (save the whole thing, not just a branch) or by typing 'restore point' in Start.  I have seen cases where sometimes the repair doesn't work and a complete reinstall is needed, which suggests that some registry elements might altered.  In any event, havin a restore point when you change things is a good idea.

[BrookeWilliams1]

Good tip, have done so, thanks Dan.