The following section in registry should be checked:

HKEY_CLASSES_ROOT\http\shell\open\command
Key: (default)

Most (but not all) browsers check it to determine the current browser.


currentBrowser = RegistryGet("HKEY_CLASSES_ROOT","http\shell\open\command","")
MsgBox( currentBrowser )


Some browsers could create additional section HKEY_CLASSES_ROOT\http\shell\OpenWith\command, which helps to avoid the conflict with IE settings.