Voice Problem with Gtalk while calling time

Hello,

I am facing some problem with Gtalk and Ymessager Calling time. i am using (Desktop) with Configuration XP SP 2 OS with Intel Dual Core 2Gz, Gigabite 945 Mother Board (Intel Chipset) with 2 GB Ram, i have installed all required software (Drivers). i am trying to call by system to system by using Gtalk and Ymessager i can hear Ringing sound after receiving but i am not able to hear the voice sound... what is problem with my PC or any hardware? i have check with my New Headphone it is working with other PC... plz let me know whats wrong with me...?

thanks & reagards
sandeep cc