Default [Q] Help:using p3600 trinity as GSM modem (SMS)

Hi
I would like to connect to my p3600 via USB and using winxp hyperterminal send a sms using the cell phone.
When I connect cell phone using usb cable the activesync runs.
Then I open hyperterminal and connect to com4 (not sure. I saw it in activesync)
I launch the command:
AT
It returns OK.

I disconnect cel phone and the AT command returns OK again. I close active sync and AT command returns OK.
It seems that hyperterminal e not connected to cell phone.
Where can I see the com port of the cell phone?
Hoe to setup theses things properly?

Thanks a lot

Alan