It's now 2020. As an update to this 2 year old discussion, CS1, CS2 and CS3 are officially dead and the activation servers are gone.
The opportunity to receive a replacement serial number and activation-free installer ended last year. After 12+ years, it's no longer possible to re-install CS3.
Creative Suite is no longer legally sold by any vendor, retailer or country.
OPTIONS:
Photoshop or Premier Elements 2020 (approx $100, no subscription needed)
https://www.adobe.com/products/photoshop-elements.html
Creative Cloud Photography Plan (approx $10/month for 1 year subscription)
https://www.adobe.com/creativecloud/photography.html
Creative Cloud All Apps Plan (31 + apps & services)
https://www.adobe.com/creativecloud/plans.html
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Beware of fake Adobe reps who may contact you privately offering to sell you software or take control of your computer. It's a scam, run away!