I've been trying since forever to do it. How to do this?
Root the mobile, search on XDA forum on how to root your particular device. Every device rooting technique is different... Go through comments, reviews before rooting.. Once you have successfully rooted, download application eg: "system app remover" or similar apps. Open the app and now you uninstall your google talk app.
It is not possible without root because it is a system app & you require sudo permission to uninstall it. In upgraded version of mobiles these days there is option to disable system apps.