I'm not aware of any official download. If you bought it online as a download back in those days, it may be listed on your account, but otehrwise you'll have to scour the Internet or ask around with friends....
AngryJane please see Looking to activate Creative Suite 2, Acrobat 7, or Macromedia products? - http://forums.adobe.com/message/4919014#4919014?sdid=KCHDS where this topic has been discussed.
Angryane if you have tried the serial number on the download page then it is likely you are facing other difficulties such as possibly a permission issue as part of the install process. Which operating system are you using? What other Adobe software are you using? Do you use any type of migration assistant or ez transfer to bring over your files and applications from your other computer?
No other software. Windows Vista. What kind of permission issue? I just did an install and tried to enter the serial number when the program requested it and it said the serial no. was invalid. I'm a graphic artist, photographer, not a geek! BTW I use Firefox.
Will it is likely that it is having difficulty writing to the Adobe Registration Database. You can find details regarding it's location at Error "user name, organization or serial number is missing or invalid" |Photoshop CS2 | Mac OS - http://helpx.adobe.com/photoshop/kb/startup-error-photoshop-cs2-mac.ht ml.