It's odd that you would be rerouted to the myidentit portal. That is typically for verifying student status. Is your CS3 an education version? Also, are you sure you're entering a serial number or is it perhaps a redemption code? Redemption codes are used when you purchase software from a third party reseller. They are typically alphanumeric and are entered once to get your serial number, which numbers only. I ask because entering a redemption code might take you to the myidentit portal to verify education status, but a serial number shouldn't do that. I would recommend going over the suggestions in this help document to see if you can verify/recover your serial number: Find your Adobe product serial number quickly. I know you said you don't remember your account details, but perhaps you can make a guess at what e-mail you were using 10 years ago. Your e-mail address = your Adobe ID, and you can use it to Sign in - Adobe ID to get the serial number. I doubt there is anywhere you can go in person with the disks and box to get the serial number. Again, if you purchased CS3 from a reseller, the numbers on the packaging are probably redemption codes, and you have to go through the steps in Find your Adobe product serial number quickly. If you purchased directly from Adobe and the numbers are indeed a serial number, you should be able to enter it when prompted during installation without a redirect to myidentit. Incidentally, since you don't have a CD drive on the new computer, you can download CS3 directly and install that way: Download Adobe Creative Suite 3 products​. Make sure you download the exact version you own (ie. CS3 Design Standard not one of the other links). Your serial number will only work for the suite you purchased. Finally, Szalam is right that CS3 may not run on the newest Mac operating system, which is El Capitan. CS3 is nearly 10 years old and hasn't been tested on modern operating systems. That said, it's worth a shot, especially for us cash poor types.
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