Hello,
Often when several NICs and several clients have been installed and removed, the network settings in the registry get hosed, essentially pointing to things that no longer exist. Search the registry for NetTran to see the settings, often there will be a 00 and 03, without 01 or 02. . .
Another way things go off is Windows Profiles, especially when installed after many months with one user. Thirdly, hardware profiles settings can affect network settings, though usually on portables or machines using USB NICs.
To correct the situation, first ascertain which scenario above is the most likely culprit. Remove the network components from the bottom up, and actually remove the modem and NIC during the reboot phase. Order of procedures is important, as removing the hardware first, then the network component is very likely how this problem occured in the first place. Remove the software while the hardware is physically present, then during the restart, Power OFF, remove the Hardware, then restart. . cheers.