UltraVNC for Windows

UltraVNC is a powerful, simple-to-use and free software that displays the screen of another computer's screen (via internet or network). You can use your keyboard and mouse to control the other computer remotely. This allows you to work remotely on a remote computer as if it were your own, from your current location. You can access the computers of your customers from anywhere in the world, and remotely resolve any helpdesk issues, if you are a computer support provider. SingleClick add-ons make it easy for customers to access remote helpdesk support without having to install software or follow complicated procedures.

Key features: File transfer, Video driver, Optional Encryption Plugins, MS Logon, Text chat, Viewer Toolbar, Java Viewer with File Transfer , as well as Auto scaling and Server Side Scaling, Multiple-Monitors-support,Repeater/Proxy-support, Auto reconnection, good performances and tons of other functionalities.