VS 2010 [RESOLVED] Doesn't recognise Imports System.Speech.Synthesis

I am using VS 2010 Express.
When I try to type "Imports System.Speech.Synthesis", intellisense fails when I get to "Sp". I continue typing the full line and I get the error:
"Namespace or type specified in the Imports 'System.speech.synthesis" doesn't contain any public member or cannot be found. Make sure the namespace or the type is defined and contains at least one public member. Make sure the imported element name doesn't use any aliases."

I can't find any explanation why I can't access System.Speech.Synthesis on the net. Is this another instance of the free version missing functionality?