We are using prism for developing WPF applications. The 4.1 version supports only windows 7 and windows server 2008 as per the following link
This begs a question. As far as I know specific operating system support is only required for assemblies with legacy code. If the assembly is completely written in .NET it just need the .NET frame work support as this itself is a "virtual machine".
If this is true is prism contains legacy code?