How did you transfer it? Did you try re-installing it from the installation discs? Adobe puts a lot of stuff in the application support folder inside the library (root one, I think), and their apps won't run without those files.
I'm kind of lost. What did you get when you bought it electronically? An install image file? Did you not keep a copy of the file? Can you contact them and ask to be given the file again to use with your license?