How do I recover a lost Serial No?

Last week our computer crashed and died. We have just had a new one built to our needs. I use CD10 which was an upgrade from CD7 full version. CD10 refuses to load and I can't find the serial no. for CD7. I registered it when I bought it. The only Corel support no. in Australia no longer supports these earlier programs with a big push to buy the latest version. If it's registered, someone must have the no.             Does anyone have any ideas please?

Thank you

Jen in Oz