You don't use it at work?
http://www.realvnc.com/download-free.html
Install this on both machines.
Your dad should start it in server mode ("Run VNC server").
After this, there should be a "VNC Server" icon in his sytem tray. Dragging his mouse over this will display his ip address.
Get this IP address, run "VNC Listener" on your computer, input the IP address, and that should do it. It's very simple.
You can also set a password and play around with the options (e.g. don't display background so it's faster, etc.) on the server machine.
For some reason, I can't get VNC working this way between my desktop and laptop - probably because of my router/firewall. If you have problems too, you might have to connect the other way: run "VNC listener" on your computer, have your dad run "VNC Server" (as above), then have him right-click on the icon and choose "Add Client" and then input YOUR IP addy.
VNC rocks.