In general, you can install it on two computers. The place to look to find the answer is the Software License Agreement, also called the EULA. This agreement governs the use of your Adobe product, and is translated into 28 languages within each document. It also covers some basics about product activation.
So, in general, how many systems can you install Adobe software on, including CS5? The answer for individuals (as opposed to businesses) in most cases is two. The catch is that both computers must be used only by you and the two systems cannot be used at the same time. This policy was designed so that you could run (say) Creative Suite at home on your desktop PC, as well as while travelling with your laptop. But the types of computers and their usage has blurred so much now that you can just pick any two you own and the product will install and properly activate on both. For CS5 the two machines must also be of the same operating system platform (Windows/Mac), because the software is licensed and delivered for use on a specific platform.
More info at the URL below
|_MG_5100 by tim and jan|
from Welcome to the Saloon!
|The Grimm 11 year old by Ryan Gardner|
from Trick or Treat
|Heron with fish by APenza|
from A Big Year - birds