ISDN Error Message

I have a problem with a PC which when boots into Win 98 SE gives the following error message:

No ISDN devices were found. Please install an ISDN device and run the configuration wizard again.

A new user has been “adjusting” things on this PC and after which this message started appearing. Any idea’s on how to get rid of this? We have a broadband connection which is working fine as are all other applications on this PC.

Thanks in advance for any help.