Software to controle another computer far away from home

One of my friend bought a Cube and I had install everything in it, but when she have a problem, it's very far from my home to go there and install or repair anything. So is there a software that will permit me to add/repair/install without going there... to see her computer in my screen and make changes?
B.

Yes. VNC.

http://www.realvnc.com

There is a Mac client, Chicken of the VNC, which I use to control my dad's PC running RealVNC, over ADSL.
http://sourceforge.net/projects/cotvnc/