Microstudio V2.517 update CDROM will not load
 

I recently purchased your microstudio V2.517 update CDROM and attempted to install it on my computer. I followed the written instructions to the letter being extremely careful to get the registration number correct but when, at the end, I clicked the finish button, I received an error notice saying it would not load because the registration number had been used more than four time already and that was the limit. I thought that, as careful as I was, maybe I had made a mistake. So, I tried numerous times to repeat the installation getting the same error and notice each time. What can I do?