How to make this computer to work with voice chat which does not support required audio compression format.?

This compuetr works with internal net work through router and computer is connected to router by wireless. While trying to connect in yahoo messanger conference for voice chat, error message comes out saying that this computer doesnot support the required audio compression format. However PC to PC works. Can any one suggested how to make the conference to work.How to make this computer to work with voice chat which does not support required audio compression format.?
On your Yahoo Messenger, click 'Actions' menu, then click 'Call Setup' to let Yahoo test your audio device.





If Yahoo cannot detect it...read on








System requirements for Voice Chat





System requirements for using Voice Chat:


Windows 2000/ XP/Vista





Pentium class processor of at least 1 GHz


Internet Explorer (version 5.5 or later)





At least 256 MB RAM





A microphone, sound card, and speakers





A non-proxy connection to the Internet


(A broadband connection is recommended, but not essential)





How do I install the DSP Group TrueSpeech鈩?Audio CODEC?





Voice requires that the DSP Group TrueSpeech鈩?Audio CODEC is installed and enabled on your computer.





This codec (compression-decompression) software is included with every copy of Microsoft Windows, but may not have been installed or enabled.





Please contact Microsoft (sorry to pass the buck鈥? for more information.