Using external player to play only .dat files and nothing else

[kevon27]

TV-Server Version:
MediaPortal Version: Release 0.2.0.0
MediaPortal Skin:
Windows Version: Xp Pro sp2
CPU Type: Amd Athlon xp 2400
HDD: 20, 60, 300 GB West Digital
Memory: 768 ddr
Motherboard: Epox
Motherboard Chipset: NF2
Motherboard Bios:
Video Card: Radeon 9500 pro
Video Card Driver:
Sound Card: Chaintech
Sound Card AC3: optical out
Sound Card Driver:
1. TV Card: pvr 150
1. TV Card Type:
1. TV Card Driver:
2. TV Card:
2. TV Card Type:
2. TV Card Driver:
3. TV Card:
3. TV Card Type:
3. TV Card Driver:
4. TV Card:
4. TV Card Type:
4. TV Card Driver:
MPEG2 Video Codec: ffdshow
MPEG2 Audio Codec: ffdshow
Satelite/CableTV Provider: directv
HTPC Case: cooler master
Cooling:
Power Supply:
Remote: hauppauge 45 button
TV: phillips
TV - HTPC Connection: component

I want MP to play all media files internally but send *.DAT files (hd dvd rips) to play with Power dvd. How can I do this?
When I set the check to use an external player, all files are opened with the external player. I even assigned .dat to open with powerdvd manually by right clicking and selecting open with and choose powerdvd. But MP still open everthing else with powerdvd..

Help please...