Vmware is a great Virtual machine which will let you run all flavors of Windows, but vmware is not freeware nor opensource.
There is also Plex86, which is another good virtual machine, this is open source and currently latest build can do win95.
On the Emu side of things wine is a sort of emu but it is not really an emulator, anyway it works great with most appz there is a list on their site of what works and what does not. There are probably others out there i dont know about but do a search at www.freshmeat.net and you are sure to find loads of stuff.
Why do I use LINUX ? Cause its the BEST OS
Why do I use Windows? Cause its the BEST Nintendo..