I have headphones connect IT biohazard and the left handset is less louder than the right and yes it is a computer no headphone. Please don't know what to do next and it annoys me already.
Which audio connector has 3 contacts (headphone jack and separate microphone jack) or 4 contacts (headphone and microphone in one) on your computer? Check the "balance" in the sound settings, ie stereo balance.