This article claims that it is possible to install .NET on those two operational systems. I haven't tried it yet, but it looks possible. This strategy is related to the fact that MS does not want to give support to WIN98, forcing users to upgrade. The JVM runs on WIN98 and NT so it is not make sense not allowing that C# runs on Windows 98. Maybe all that web programming crap named ASP.NET does not work well, but who cares?