Protocol Association for Windows.
Windows Registry Editor Version 5.00
[HKEY_CLASSES_ROOT\xxx]
@="URL:xxx Protocol"
"URL Protocol"=""
[HKEY_CLASSES_ROOT\xxx\shell]
[HKEY_CLASSES_ROOT\xxx\shell\open]
[HKEY_CLASSES_ROOT\xxx\shell\open\command]
@="C:\\xxx.exe"