NHibernate which cache to use for WinForms application
SysCache uses the "ASP.NET" cache only because it's the only one included with .NET 2.x/3.x (.NET 4 includes a separate System.Runtime.Caching assembly)
It can be used in desktop applications without any problems (I'm using it right now), and it requires almost no configuration.
Now, your memory considerations seem to be a little off with this century. No machine has shipped with less than 1GB in the past years, and most have between 2GB and 8GB, so 80MB is essentially nothing. The browser in which I'm writing this takes 220MB.
The very essence of caching is about using a resource (usually memory, disk in very particular cases) to reduce the usage of a slower one (network)