Retrieve Photoshop CS4 serial ...

Heyho,

I'd like to reformat my MacBook's drive because it's totally cluttered up. Now, just before I hit delete in the Mac OS X Installation Disc's Disk Utility, I realized that I don't know the serial for my copy of Photoshop CS4 anymore.
I bought Photoshop online, and they sent me an email telling me the serial number, but in the meantime I changed my email address, didn't copy all emails from my old account to the new one, and don't know the old account's password anymore...
I obviously don't want to buy Photoshop again, but I can't find a way to find out the serial number Photoshop was activated with from within the app. Is there anyway I can do this?

P.S.: I tried googling about this matter, but the results were pretty much all about pirating Photoshop...

 

Oh yeah, they actually have a help page for that...

*faceplants* - why did I not think about this earlier?!