BleepingComputer.com: "failed" Network Diagnostics

Running XP SP2 and connect to internet thru Motorola SB5120, Linksys WRT45G router, and D-Link DGE530T eternet card. Motherboard (ASUS A8N-E) also has on-board eternet connection not in use (currently disabled, but have used it OK). Comcast is service provider. During the process of troubleshooting intermittent slow connections, ran Network Diagnostics (even though internet connection was at normal speed at the time) and there were two "FAILED" messages returned: one for Surfboard Modem and one for Toshiba PCX modem which hasn't even been installed for months. Of course, neither of these are listed in Device Manager.

My question is: how can I "clean up" my network adapters listings to eliminate these obsolete items or would it be best to just leave them alone since internet connection does seem to be working OK most of the time?

I have read most of Microsoft's support articles on troubleshooting TCPIP issues and hesitate to use their "reset" tool and risk having to start over configuring the network and related programs as they suggest might be required. I'm not an expert with the Registry, but don't mind working with it if need be.

Thanks for any suggestions!