How to install Adobe photoshop without original discs, install from copied files only?
You won't get a working installation by copying the binaries from /Applications and will want to re-run the proper installer or get assistance from Adobe since this is a licensed product that has proper vendor support for reinstalling the licenses if you should need to move it from one computer to another.
If you for some reason lost the installation files, you can download the trial here: http://prodesigntools.com/download-adobe-cs4-and-cs3-free-trials-here.html
Once installed, simply register with the credentials you received upon purchasing the product. If you do not have your registration details either, I would suggest chatting with an Adobe representative to discuss your options: http://helpx.adobe.com/x-productkb/global/find-serial-number.html (simply click the Chat Now button at the bottom of the page).