Sorry because I have to use English this time...
anyway... your email account is in Yahoo! that means, it won't work with MSN or Windows Messenger,, because MSN & Windows Messengers are made for Hotmail or Netpassport accounts
so .. you should sign up for an Email account in Hotmail or MSN
for Yahoo! messenger with voice.. that's very clear & simple ...
you can read "with" .. which shows that voice is one of the features of Yahoo! messenger..
yahoo! messenger is just like MSN or Windows Messengers..
but you must always remember that MSN or Windows Messenger users cannot
chat with Yahoo! Messenger users.. because they're totally different programs ...
I hope that I helped you.. sorry for using English but I'm forced to do so..