Vista - live messenger 2009 audio problems

Can anyone help please, when I have installed live messenger 2009 I am unable to communicate via voice, it says ' no sound card detected ' messenger 8.5 works fine and doesnt give this error. My computer does have sound and as stated works fine with 8.5 Has anyone else come across this problem? Can anyone help please as I would like to have live messenger 2009 installed and working properly. I have tried totaly uninstalling 8.5 then installing 2009 same problem, tried another reinstal same problem , put 8.5 back on and 8.5 works fine.