How to take a value from Regedit using .NET 3.5?

I already make a web server than works, i create it to use it in a game i'm making on, i do them all the time using .NET 4.0 in VS in my work for business apps, but the problem with this server in particular is the fact than i need to downgrade the framework, and because of that there is one little part of the server than it broke itself.

How can i read the regedit using .NET framework 3.5 or under?

I'm asking this here because this is necesary for make the librarys who allow the comunication between unity with the game server compatible actualy compatible with unity.

Any comment, question or request for clarification as long as will be constructive and/or helps to find the answer would be much apreciated.

Thanks in advance