I swear, we had a vista sticky somewhere.
*****If its a new Windows PC:*****
www.windowsupdate.com Get your updates. Keep going back till it tells you you have none, even get the optional ones.
Then->
http://www.microsoft.com/downloads/deta ... 6652cd92a3
Download the web-updater from there for directx and run it.
restart your pc. be happy, it should work. if not, come back.