Is it possible for me to install Rhino on both my desktop pc and my laptop?

You may install Rhino on two machines (desktop & laptop), however, they cannot be used simultaneously. The Rhino End User License Agreement (EULA) states:

"No more than one person may use the Software {Rhinoceros} at any one time. You may freely move the Software from one computer or location so long as there is no chance of the Software being used simultaneously at more than one location."
Rhino Newsgroup