Les,
Sorry mate.. I may have given you wrong info!
I have my Keyspan set to COMMS 1 ( ST4 basic will only see Comms 1 or 2)
The SBiG CCD.exe doesn't work for me! ( I thought it did, but I've just ran it - doesn't communicate!!)
I can successfully talk and operate the ST-4 as an imaging camera under AstroArt4, the ST-4 plug in works well.
Sorry for the confusion.
[EDIT] I was sure there was a program I used...
http://www.sbig.com/sbwhtmls/ImCap.htm
Imcap is a freeware program, runs under XP and controls the imaging from the ST-4; I've just re-installed it and it works 100%