No, there is not a problem enabling 6 channels and ProLogic2 on the 410. Here is how you do it in Windows XP:
To enable 5.1 you have to go into the windows control panel for "sounds and audio devices" (the windows mixer) and configure these options:
1 "Use perfered devices" - check this
2 "Delta 410 multichannel" -select this
3 "5.1 speakers" - which is selected by pressing the "advanced" button, under the speakers tab. There is also a setting here for 7.1 speakers, but when I select this WinDVD only gives me the option to select 2 speakers, not all 8 so make sure you use the 5.1 setting.
Once you setup the windows mixer as above, go back into WinDVD and click on the Audio Setup and you should find that you now have these settings:
2 speakers
4 speakers
6 speakers
The last two (7 and 8 speakers) are greyed out and a message I received from Cliff states that WinDVD will have to be coded to recogize the Delta 410/1010 in order to use these outputs.
However, you now have Dolby Prologic2, AC3, and DTS decoding just as in PowerDVD.
NickB