People cannot hear me - Logitech Webcam

If your webcam has a built in mic make it the default mic

XP
Control Panel (Classic View)

Plug in your webcam

Open 'Sounds and Audio Devices' folder and click on the Audio tab - make your webcam mic the default device in the 'Sound recording window'
Open 'Volume' below the window to ensure the mic is not muted
Click 'Apply' and 'OK'
Restart your computer

Vista

Plug in the webcam

TEST SPEAKERS
Right click on speaker icon in System Tray or from Control Panel
Select "Playback Devices"
The speaker icon ( checked as working) and volume level graph should be visible
Right click on the volume graph and click "Test"
Left hand speakers followed by right hand should be heard

SET DEFAULT & TEST MIC
Click "Recording" tab.
Right click on the volume graph and select 'Show disabled devices' and 'Show disconnected devices'
To set required (webcam) mic as default - click on mic font to highlight and click "Properties"
In lower dropbox display "Use this device enable" click 'OK'
Click "Levels" tab and ramp up sliders ( adjust to suit later)
Return to "Recording". Test mic by speaking and make sure volume graph displays

Restart computer

Configure your webcam to the chat program

Try msn audio video test in the msn bar menu, chose the mic source.
if it's steel not working try another mic.
if not you have maybe a driver or card sound problem