If you installed Google Talk, or more commonly known as GTalk on Windows Vista, then you may face a problem, if the installation is not done properly. You may notice that only one user (administrator), will be able to login to Google Talk, while others will not have permission to login.
This happens because of the extra security setting Microsoft has introduced in Windows Vista. In order for every user on a Windows Vista machine to be able to login and use Google Talk (Gtalk), the following steps will help:
1> Uninstall Google Talk (Gtalk), if you have already installed it.
2> Download a fresh, latest copy from http://www.google.com/talk/ and save the file on your desktop.
3> To install Google Talk (Gtalk), right click on the installation file (googletalk-setup.exe) and select Run as administrator.
Google Talk installed in such manner will be available for all users who use that particular Windows Vista machine.
To uninstall Google Talk if it has been installed for all users :
1> Go to Start menu, find Google Talk folder, Right click on the Uninstall Google Talk shortcut
2> Select Run as administrator and follow the instructions till you are done.