mfs42.dll file missing

Installed a new modem, did some cleaning up of the HDD on an ‘older’ PC using Windows98 OS…
I must have removed the msf42.dll file, how escapes me as I have no traceable record of it… Every time I try to open an application I get an error message ‘cannot find msf42.dll file’ would like to now of a work around or do I have to reinstall 98… All help greatly appreciated…
BillG