Zelandakh is right on this one - VNC is a good solution and it is free. We use it to support our customers via VPN connections as well as in-house support (the server is not that far away but I am getting lazy in my old age!). I have used PCAnywhere, Carbon Copy, Remotely Possible, ManageWise and VNC has been the easiest to implement. A nice feature of VNC is that it supports cross-platform remote control (remote control only - no file transfer, chat, etc.).