If you have a Nokia mobile phone and Windows Vista on your computer – then sending and receiving mobile text message just got very easy. Nokia Text Messenger allows you to receive and send messages from Vista Sidebar
You can read latest mobile text message on your computer screen. You can also write new or reply messages on your computer and send then instantaneously.
Nokia Text Messenger application fetches you the latest text messages from your connected Nokia device. You can keep this gadget on Windows Vista sidebar in small format.
For easier reading and sending of messages you can float the bigger sized display box on the desktop. To use this gadgets, you need to have Windows Vista and Nokia PC Suite version 6.85 or later installed on your computer.
Details:  Nokia Text Messenger -  More Information
As pointed by Nicko, after you download and install Nokia Text Messenger – make sure your Nokia phone is connected to computer via USB or bluetooth. Now your are ready to interface and play with your Nokia Phone Messaging with this Vista Gadget.