Modem acting up on PIII800

A client just called who is having problems with his modem on a new PIII800. Before installing a scanner, printer, web cam and digital camera his modem worked fine. At this point it dails normally but for 1 exception does not connect. Im a bit weak on hardware so bear with me. i need to look at this system in the morning. The first thing i want to do is check the device manager for conflicts,,what if i dont find any? The second thing i wqas going to do is uninstall the devices one by one,then trying to connect. Am i on the right track here? I dont think this is a difficult problem but i want to be prepared. Any other tips is appreciated.

thanks