"The Magic Number Database": I recently discovered magnumdb.com (cleared virustotal 30-9-2018) in a tweet from Remko Weijnen. "The Magic Number Database" is apparently maintained by Simon Mourier.

Looking up your error code: https://www.magnumdb.com/search?q=-2147021886

1 ERROR_SUCCESS_REBOOT_REQUIRED Int32 -2147021886 %ProgramFiles(x86)%\Windows Kits\10\Include\10.0.17134.0\shared\winerror.h(11960,0)

Other Approaches: Including a couple of other options for similar situations.

1. Visual Studio (2017): Menu choice: Tools => Error Lookup. This Visual Studio tool (errlook.exe) can be found in the "Tools" folder of your Visual Studio installation. N.B! Localized messages! (internationalized).

   

2. cmd.exe: Via the command line, the net command can normally be used to look up error codes: net helpmsg errorcode. See blog link below for limitations.

3. certutil.exe: Try it via cmd.exe: certutil.exe /error errorcode. Not sure if this is available in a clean install, but with Visual Studio it should be already available. Appears very good! Localized messages.

4. Err.exe: An old tool from the Exchange team. Dated now. See blog link below - in the comments. Needs download. English messages, non-localized.

And in C++ the FormatMessage call. And just mentioning the winerror.h and ntstatus.h files. Retrieving the Last-Error Code. And a Powershell blog.

calc.exe: And obviously use the new Windows 10 calc.exe in "Programmer Mode" to convert between hex / dec and all kinds of other tasks:

• https://blogs.msdn.microsoft.com/oldnewthing/20170919-00/?p=97046