Hi Cindy
You can still use Yahoo messenger for IMing your friends. But some services like voice and webcam may not work! To check you can turn on the inbuilt firewall for Internet explorer and try to use yahoo messenger
Here is how to do that
1) Go to control panel and find the network connections and open tha
2)You can find your active internet connection there(If you are connected to internet at that time), right click on it and click the advanced tab to find about the firewall
You can later turn it off doing the same thing
Hope this helps
Siddhaart
p.s: Even though if you use a firewall you can always disable it when you use messenger service