Gtalk Autoreply is a free and simple utility for windows to set an auto reply for Google Talk. You can use this to inform your friends that you are not at your desk when they ping you. All you need is to login with your Gmail user name and password and the utility will sent an automated message when any one pings you. This utility can also be started at Windows start up. You can type in you own auto reply message.
When any one pings you after you have enabled this settings, they get the message which you have set in Auto reply.
Gtalk Auto Reply is a simple and very useful utility for all Gtalk users and its worth downloading. The author is also the developer of TweetmyPC, which can shut down the PC using Twitter.