lost FCP serial number

Hi stop me if you have heard this one. I am in the process of installing FCP on my new IMAC. I have my old version 6 upgrade i bought two years ago and then i plan to install the 7 upgrade. I started the install and entered my serial number. The problem is it is asking for my original FCP serial number from FCP 3 when I first started out years ago.

The problem is I moved and now can't seem to find it.

Is there any way around this? I am totally by the book and this is not pirated software. I just can't find my old FCP box. I looked on my Powerbook which has 6 installed so I thought I could find it there. No luck just the last upgrade serial number.

If anyone can help I would greatly appreciate it. Thank You