Remote controlling a computer is already a common activity and in some cases it's practically mandatory because it's the only way to deal with a buggy machine over the Internet.
In case the 'Remote Desktop Connection' tool included in Windows is not enough for you, UltraVNC comes into play as one of the most powerful software solutions in the market, providing almost everything you could ask for for remote administration.
The installation process is the moment when you'll be prompted to choose how exactly you intend to use UltraVNC, as a server, as a client or both. Of course, there are also many other configuration steps you can customize, but it's better to leave all options the way they are if you're not an experienced user.
Using UltraVNC as a server will require two different passwords, one for full control of the computer and one for the view mode only. As a client however, you'll need the server's IP and the password to establish a connection.
UltraVNC works amazingly fast, as the whole process goes pretty smooth. Probably the most impressive thing is that UltraVNC remains very friendly with hardware resources on both computers and enables you to choose even the resolution you want to use on the remote machine.
All in all, UltraVNC seems to be one of the best tools of its kind and in case you're looking for a remote control software solution, this may very well be the number one choice.