Serial not found in cd

try to contact nero customer service,they say:
"Nero customer service can help you if you need assistance with lostserial numbers, rebate inquiries, basic non-troubleshooting issuesregarding the Nero installation process, questions about purchases, andrequesting replacement installer disc."
follow this link to go to nero's customer service site:
http://www.nero.com/ena/support-customer-service-contact.html#tab2

hope this will help you.

I am sorry to bear bad news in here, but when you lose the key, there is no chance to get a replacement number from the distributor. If you lose the software serial it is the same as if you lose the whole product. When that happens you cannot install the software anymore, unless you use one of the illegal pirates serials available on the Internet. But for obvious reasons I will not suggest you going in that direction, the copy won't be genuine, and serials' websites often carry malaware.