I finally configured an adhoc connection at windows startup.
I’ve done it on Windows Vista Home Premium. I used a scheduled task. After creating an ad hoc wlan connection with the software included in the wlan usb key, make it active is done with this command:
netsh wlan connect name=”My-Adhoc-Connection-Name”
So i configured a scheduled task activated at windows startup and executed by the user SYSTEM that runs this command.