This is from memory (can't access the computer w/ vv4 on it now)...
Bring up the control panel for the SC. Go to the last tab. There's a checkbox for something like "allow multiple interfaces" or something like that. Check it and I think you'll have to reboot.
Once rebooted, bring the control panel back up. Pick 5.1 sound. Note the outputs for each channel. In vv4, go to the audio properties page (under options?) and pick the Santa Cruz as the output device (rather than the MS mapper).
Finally, create a 5.1 audio project, click on the mixer symbol in the upper lefthand side of the mixer window (the symbol is the point with 3 arrows pointing right coming out of it). This will let you map the channels to the santa cruz channels.
In the souncard control panel you can see a graphic of the ports and what is assigned to them. Make sure you have it mapped correctly and the speaker node is set correctly.
For AC3 output you can use the six outputs on the card.
1) Set application output mode to either 6 speaker or 5.1 audio output. Then set 6 speaker mode on Santa Cruz CP Main Tab. Be sure to set Virtual 5.1 to off.
2) Rear powered pair to ch 3/4
3)Center powered to black or white RCA plug coming from Versajack (channel 5)
4)Powered sub to red RCA from VersaJack (Channel 6)
5)Front powered pair to front output (channels 1/2)
Alternatively you could set the VersaJack to digital out and use an external decoder.