One of the most common requests I see on the VS extensibility newsgroup (and in my Inbox) is "where can I get a version of flex and bison that will work with the VSIP Language Wizard"? Here is how I recommend you set up your machine if you plan on writing a language service for Visual Studio using the VSIP Language Wizard:
That should be enough to compile and test the "default" language service (a stripped down version of C). You can change the .lex/.y files in the wizard to compile your own language service. See the Babel package & documentation for more information. Hopefully this will get you well on your way to hooking your own language into Visual Studio!