"... on a backup XP machine ..." Which says to me you're not running anything on the XP (just hate to part with old HW) - think about loading Linux on the box and using a package called Mochad. Then from a Bash script (php, C, Python...) you... echo "pl G4 on" | nc localhost 1099 that is if the CM15 in plugged in there, if not you change localhost to [otherhost] and it works just fine.
cal