Seems all you need to do is go here: http://www.adobe.com/cfusion/entitlement/index.cfm?e=cs2_downloads&pid=4485850 , register an account and you'll be provided with download links and serial numbers.

To avoid resorting to piracy I've been using a mixture of Paint.net and GIMP for my photo editing needs, but adding a slightly older Photoshop to my toolbox will certainly be welcome.