Flash installs into the OS... that's why its various elements (such as plug-ins) appear in the OS's Add/Remove programs. They have to register themselves into the OS registry so they can be accessed from any program on the system... so simply copying a plug-in file from another computer won't "install" it into the new one. I think there was a time once when Flash plug-ins were indeed largely stand-alone and could be copied into each browser's "plug-in" folder, but that was years ago.
