WHEN I TRY A SKYPE TYPE CALL I CAN HEAR THE CALLER FROM BOLIVIA BUT HE CANNOT HEAR ME. HOW CAN I FIX MY SOUND?

I have been using Skype for over 3 years with very good results.
Make sure you are using the latest version of Skype (version 3.8)
Version 3.8 works better than all previous versions.
When your Windows Firewall prompts you that Skype want to access the Internet, say “yes” or “allow” Skype to access the Internet. Some antivirus programs will block Skype too, unless you specifically tell them to “allow” Skype through firewall.
Check your Skype Audio settings at:
Tools–> Options–> Audio Settings
Make sure Skype has your microphone selected.
Make sure the microphone volume is all the way up.
Turn on (select) “Let Skype adjust my audio settings” –
“Save” all changes…. see if that helps.
While in Skype Options, also check the Advanced–> Connection Tab settings.
Try turning on (check box) “Use port 80 and 443 as alternatives for incoming connections”.
Also, while there, note the random Port assigned by Skype.
It is labeled “Use Port xxxxx for incoming connections.
xxxxx is a random port number generated during your installation of Skype.
If your PC is behind a NAT-Router, you will need to make sure you “port forward” or “port trigger” on that port number assigned by Skype. Doing this will give you the best possible connections using Skype. That is how I use Skype.
Enabling ports 80 and 443 are only a work-around for Skype if your can’t get around your firewall port blocking.

try stopping firewall on ur computer.If that doesnt work , check your mic , if its working.go to start/control panel , sounds/audio device and run a trouble shoot.