doctor,
Now I think I know who sent the PM that I goofed and deleted! Sorry 'bout that.
Look for "AGWPE.zip", it's the free ('hamware' license) program. It configures the sound card into a TNC to use with most of the digital programs. There's also a file of drivers that you may/may not need, get it just in case.
Very basically, you need a patch cord from the sound card input (mic) to the radio's output, or speaker jack. That's the signal into the computer. Another patch cord from the sound card's speaker jack to the mic or digital signal into the radio. That one might need a isolation transformer (Rat Shack 1:1) to prevent interference problems. Wouldn't hurt to put one on the other patch cord either. A bucket of torroids for those cables may also come in handy, but try it first to see if it's necessary.
That 'AGWPE' does need to be set up/configured. It isn't all that simple, but it's also not all that difficult (hey, I did it, anyone can!). There are a couple of forums on 'Yahoo' that deal with all this, not a bad idea to take a look at them.
I don't use this strictly for packet, so can't help you with that end of it. It's a pretty generic type of thing so will 'handle' most of whatever you run with it, sort of, it ain't fool proof (it's free). If you have problems with it, George (SV2AGW) has been very helpful.
Have fun...
- 'Doc