Hello, I'm just trying to install YAF and get this error:

Error 2 Could not load file or assembly 'System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The system cannot find the file specified.

My dev machine has:

VS 2008 .Net Framework version 3.5 SP1

What do I need to do to get past this error?

You are using the wrong version of YAF -- you need the .NET v3.5 version.