How to check if a valid serial number?

Dear Sirs, 

I have a few CDs of "Corel Draw Graphics Suite X5" with serial number. 

Two of them has not in foil. But I believe that they are not used.

Do somewhere or some may check if the serial number is valid without installation?

I have a buyer for these CDs, so I'd like to know Whether have a valid serial numbers for this cd without Folin.

Thank you very much.