[color:"orange"] Do you have a TV tuner card in your computer? [/color]
Yes, I got a TV tuner card. It's not connected though.

[color:"orange"] What type of headphones do you have? Specifically, are they USB or do they plug into the microphone / headset jacks?
[/color]
Trust HS 2200, using Microphone and Headset jacks.

[color:"orange"] If you run dxdiag (click Start | Run, type in dxdiag and hit Enter), then switch to the sound tab there are some tests you can try. [/color]
Everything is running fine according to dxdiag.

[color:"orange"] I assume you already went through the Control Panel sound options, double clicked on volume control task bar icon, etc and checked options and settings to see if they appeared normal? [/color]
Yes I did, all volume options are set mid to high, and all the I don't know how it's called in english, but in Dutch it's 'Dempen' are unchecked.

I tested the keyboard thing again and he didn't hear any noticable difference, to double check this, I put my speakers at highest volume, slowly lowering it. My friend didn't hear any difference in volume.

[Linked Image from miniprofile.xfire.com]