I lost my serial number and need to reinstall Photoshop. I never had a disc.

Hi,

I'm totally lost here. My computer hard drive was corrupted and I ended up having to wipe it and reformat with master CDs.  I lost a lot of programs, one of them being Photoshop suite which I downloaded a few months ago. I don't know what the serial number was as I downloaded it off the Adobe site in the first place.  How do I redownload?