My friend has a Razer Carcharias headset and a Realtek onboard sound card in his computer. We tested the headset on two other computers and it works very well. When we tried it on his computer, it wasn't the same story.
For some reason, the microphone input is mixing with ALL the audio being output from the computer. In Skype, for example, when he plays a song or is in a game you can hear everything he's hearing as well as voice. I tested it in sound recorder, and it does the same thing. When you play a song and talk into the microphone, it records both. I've gone into the Realtek settings and tried changing every single audio channel as well as reinstalling the drivers but to no avail. I know it's not the headset because we tried it on other computers and it doesn't do this.
But what I don't get is if all the output sound is mixing with the microphone sound and being fed back in, then shouldn't there be an echo in Skype when someone talks? When I talked with him over Skype I didn't hear myself echo, but I did hear when he played a song or started a game.
Theres a setting somewhere in the Windows Contol Panel -> Sounds and Audio Devices that has a setting called "monitering", which basically records all input that comes from the microphone and outputs it to the output device (in this case, the headset). Make sure that setting is off.
I also had this problem and did a tremendous amount of work trying to resolve the issue. I have a lot of experience in sound engineering and tested everything possible. I literally spent 30+ hours trying to figure this out and have read 20+ threads of people having the same issue with no resolution.
I have finally resolved the issue. I have an antec 1200 v3 case and I was using the rear audio out jack for my speakers and the front 2 ports for my headphones. I have finally concluded that the issue is the front audio ports are not shielded and or have intersecting input/output wires. I ended up connecting my speakers to the front port and my headset (output and input) direct to my mobo from the back of my computer. This has fixed the issue 100% for me. Hopefully this will help!