WMRX can be used on computers where WinPCap doesn't work. For example, some people have problems with WinPCap in Windows 7 and some firewalls prevent WM Recorder from using WinPCap.

ADA is a default recording mode. It should be used in most cases. If you have problems with it, you can try other modes.

PRO mode allows to capture packets coming to your Windows Media Player and Real Player. A content provider can't detect you using a stream recorder when WM Recorder is in the PRO mode. I use this mode for recording some secure streams, live streams and Windows Media playlists.