Recently a friend setup Skype on my Windows XP Professional computer. To talk over Skype I purchased a Logitech microphone headset. All seems to be working correctly, and I can hear other callers and also Windows system sounds (such as the Windows XP startup sound). However, other people cannot hear me. I have tried adjusting all the settings, and followed the Skype instructions, but still to no avail. Is it possible that I have faulty headphones?