IBM 300GL and ESS2838 modem

I have a client with an IBM Personal Computer 300GL and an ESS2838 winmodem. The modem installs on com5 and diagnostics show it works ok. Dial-up networking says no modem is installed (also hyper terminal). I went to MKB and found a couple articles about rebuilding telephon.ini and confirming a registry entry at HKLM-software-Microsoft-Windows-current version-telephony. Did what was suggested and it had no effect. Flashed BIOS with no effect. Reinstalled modem and dial-up networking with no effect. If you have seen this problem before and know of a solution I would be grateful for your help.