I have the exact same problem described by sbarella with a Tosh Tecra S1 (XPP) with its standard built-in modem card / software modem AMR.. It is normally associated with COM3 (and I see all COM ports up to 256). Changing the port makes no difference. The "Query Modem" always produces "The Port the modem is attached could not be opened. Check Device Manager etc." The unit has worked ok for about 12-months with no new software added. Then it refused to work. It is not normally left plugged into a phone jack. I have re-loaded drivers. I have checked all running processes and apps which may be trying to use the modem - they don't seem to be. I have disabled Symantec NIS-2003. I have disabled all networking interfaces and Infra-red. It still will not work. I upgraded to SP2 - modem still refuses to work with a 633 error. Device Manager status is "Working Properly" The Windows Troubleshooter is certainly no help. I have disabled the modem, rebooted & re-enabled the modem. I have deleted the modem entry in Device Manager and re-booted. The hardware is found and reported as installed correctly. About the only thing I have not done is delve into the Registry. I have put a USB modem on which is allocated COM4 and that works ok. But I really need to make the internal modem work.
Any ideas or comments would be great.