Like jeff said in several other posts as well getting hardware information is beyond this scope.
I however also needed to know the Serial port that my dial up connection uses. This information is stored in the registry
namely "AttatchedTo" gives you the COM port name.
If you have multiple devices (multiple modems that the same dialer uses) this information is also stored here in incrementing registry entries '0001' '0002' etc
I used this to change the APN as i'm using a dual SIM GPRS modem.