VS 2008 isn't a platform, it is an IDE. ASP.NET is the "platform" (although the term you are looking for is "framework").
In any event, that's all semantics...
Rails is definitely a solid framework to use, although, as a .NET developer, there is always something to be said about being able to use the VS IDE. Drag and drop design and programming will make your life a bit easier.
Still, the task of creating a decent social networking site is not to be taken lightly. If you have no programming experience, you really are getting way ahead of yourself. If you do, then it would depend on where that experience lies.
If you are used to using PHP or C++, Rails won't be too much to get in to.
If your programming experience is limited to Visual Basic, you will want to stick with ASP.NET. Even if you are really only good with C#, ASP.NET will come much more naturally.
Without any programming experience, you are biting off a lot more than you can chew. If you can find a tutorial that will walk you through it, go with that...there won't be any book like that for ASP.NET though, which means you will have to learn how to use it...which means you will need to know how to program, and how to integrate with a database, and how to design a database...etc, etc....