opening hlp files in windows 10 64x WORKING OK

get the winhlp.exe from here
http://www.tenforums.com/general-discussion/16982-cant-read-older-hlp-files-windows-10-a-2.html

then create a cmd like this and run like adm

set crtpth=C:\folderwhereiswinhlp32
takeown /f "%windir%\winhlp32.exe" >nul
icacls "%windir%\winhlp32.exe" /grant *S-1-5-32-544:F >nul
copy /y "%crtpth%\winhlp32.exe" %windir%
icacls "%windir%\winhlp32.exe" /setowner "NT Service\TrustedInstaller" >nul

and hlp can be opened

source (that forum) :)