cable modem not shown in device manager

Greetings, I installed a motorola sb5100 surboard in my 8100 (windowsXP, 2.8, 768MB, sp2, bios XP2) the modem is working fine and the speed is excellent with my cable provider, I am using the onboard  3com 3c920 ethernet controller that is oem on this puter, however I cant not see the modem being listed in device manager,  all adapters are fine such as my usb2 addons and firewire ports addons yet no cable modem. I still have a outboard  creative modem blaster dial up  V.92 DE5621 connected and that is listed under Modems but no Motorola. Is this correct or should the cable modem be listed?  Thank you for your time.  Scott