If you are using a Vista Gadget (or some other notifier) to show when you have new mail in your Gmail account, then Google Talk’s mail notification becomes unnecessary. To diable notification for new mail in Google Talk, follow these steps:
1. Open the Google Talk application.
2. Click Settings.
3. Select Notifications from the left pane.
4. From the right pane, go to New email and uncheck the Show notification checkbox.
5. Click OK.