A customer who doesn't want / can't emotionally bear / can't afford ? to upgrade one workstation?

Well if it's 'doesn't want / can't emotionally bear', then there is a solution: Citrix Metaframe, with client support for Windows 3.1 and 3.11.

I can't tell you all the steps to get there in the space provided, but you need to have an NT Server with Citrix's product loaded and able to "see" your application ( either loaded on same server or connected via LAN to the NT server ).

Refer to Http://www.Citrix.com