Still having problems with a pair of Skype USB phones, making calls either in the UK or abroad. I get my own voice repeated at the other end, but the person I'm calling (in the UK) doesn't have any such problem and doesn't get this repeating. We both have the same type of phone.
I can understand this happening when I call my daughter in New Zealand, as she just talks in the general direction of the computer and webcam!
I've tried changing the Sounds and Audio Properties from RealTek to USB Generic, and also changing from 5.1 sound to no speakers, but no matter what I do I still get lots of crackles, sibilance and echo.
I recently bought a USB phone to use with VoIP services. I set Generic USB Device in all the sound settings as the USB Phone has it's own Sound Card and it seemd poimtless by-passing that. I no longer suffer from echo at all.
Have you opened Control Panel - Sound/Audio and then gone to the Voice tab and under Voice Recording (ie your voice going out through Skype) gone through the diagnostics under the Buttons: Volume Advanced Test Hardware
Your voice volume going out may be set so high your getting some feedback from the other end.
I seem to remember the latest version of Skype has a 'let Skype control the sound' type setting that you could try. Under Tools / Options / Sound Devices.