Windows 10 only!
Create a plain text-file “notepad++.reg” with the below content,
then doubleclick this new file.
Reboot afterwards!
Windows Registry Editor Version 5.00
[HKEY_CURRENT_USER\SOFTWARE\Classes\*\shell\Notepad++]
[HKEY_CURRENT_USER\SOFTWARE\Classes\*\shell\Notepad++]
"Icon"="C:\\Program Files\\Notepad++\\notepad++.exe"
[HKEY_CURRENT_USER\SOFTWARE\Classes\*\shell\Notepad++\command]
@="\"C:\\Program Files\\Notepad++\\notepad++.exe\" \"%1\""