Your question is a little fuzzy. Computers are machines that use an operating system to accomplish tasks. Apple now names their operating systems (OS) after cats, thus, Jaguar, Panther, Tiger and Leopard. There is usually some overlap in the OS that can be run on a given machine, so calling a machine a 'Panther' machine isn't really very clear.

In general, if the specs on the machine meet the minimum for running a particular OS, then, you can install that OS and run the machine with it. If you wanted to run several OS's on the same machine, you would partition your hard drive and install the OS's on different sides.

To use an OS, you need the install disks which either come with the machine or may be bought.

So, in general, yes, you should be able to install Leopard on a Mac that came with Panther as the machine should be new enough to meet the minimum specs for Leopard. You'll need to decide what to do with Panther.

Bob.