I've changed computers and want to reinstall CS4. I downloaded the product from Adobe and verified my serial number. When I ran setup from the folder and entered the serial number, I was informed that the number was invalid. To be sure that the number was correct, I copied it from my account and pasted it in the serial number space. Still said invalid. What do I do? I downloaded the Master. Did I do wrong? My records show that I ordered and downloaded CS4 for $299. Then a couple of days later, I upgraded the package for the product for $331.63. I can't find the install disk for the upgraded product. Therefore, I do not know it's serial number. The software I downloaded may be looking for that serial number.