Disabling last known user in DUNs

In Windows 98SE, I have loaded system policy editor and disabled last known user and password caching. This is successful for the Windows logon and Client for Microsoft Networks logon, but it does not work for the last known user in the Dial-Up Networking logons. There is no .PWL, where is Windows storing this information and how do I disable it?? The only choice for Dial-Up Networking in Policy Editor is to disable dial-up, which I don’t want. Any Help???