CS3 activate [CS3 IS DEAD]

you can install (and use for 30 days), but you cannot activate.  the problem is on adobe's end and there's nothing you can do to fix that.

you can work around the problem, but it's more trouble than it's worth.

You can't.  😞  CS3 is dead.  The activation servers were discontinued ages ago.   Besides 17 year old software can't install much less run on modern computers.  It's too old.

MODERN OPTIONS:
Photoshop Elements or Premiere Elements (approx $100, no subscription needed).
https://www.adobe.com/products/photoshop-elements.html

Creative Cloud Photography Plan (approx $10/month for 12 months). Includes the following:

• Photoshop CC and Photoshop on iPad
• Camera Raw
• Lightroom on desktop, mobile and the web
• Lightroom Classic
• Portfolio website + hosting
• Adobe Express (free starter plan)
• Bridge
• 20 GB cloud storage (upgradable to 1 TB).
• Free upgrades for paid subscribers

https://www.adobe.com/creativecloud/photography.html

Premium Adobe Express ($10/month).

• Creative Cloud Express app (web and mobile)
• Premiere Rush (desktop and mobile)
• Photoshop Express (mobile)
• Spark Video (mobile)
• Spark Page (mobile)
• Adobe Portfolio + hosting
• 100 GB of cloud storage
• All premium templates and design assets including the collection of over 160 million royalty-free Adobe Stock photo collection.

https://helpx.adobe.com/express/using/express-overview.html

Creative Cloud All Apps (51 + apps & services) and Single App Plans
https://www.adobe.com/creativecloud/plans.html

Hope that helps.