error message my product is not a legal program

Hello

I bought a legal copy of Acrobat Pro 10 a few years back and it operated fine and I never got any registration error messages. My HDD went out and I had to install a new one in the machine. I reloaded all software including ACROBAT 10 Pro including the original registration number. It installed fine from the Adobe download site and I installed, now when I use the program I get an error message saying my software is not a legal copy. I checked the registration number I entered and I entered it as on the box. Any suggestions as to what is the issue? I am a registered user on the adobe site.