You can record Windows Media streams with WM Recorder in the PRO mode or with freeware WebVideoCap. Both programs can capture packets from your Windows Media Player, so you won't be "detected".

If you don't care much whether you can be detected, you can use many video stream ripping programs. For example, Replay Media Catcher can perfectly record kanaalxxx.nl adult videos:
Tutorial: How to record adult/sex/porno video streams from Kanaal XXX with Replay Media Catcher