CS3 Design ME

The ME version was never supported by Adobe. 

The CS3 activation servers were taken offline.  You would need to get a replacement installer and serial number that does not require activation.   See correct answer below for details.

Re-activating CS3 (Updated)

Do not attempt to register your legacy CS3 product either because those servers are gone too.  And owing to its advanced age, CS3 may or may not run on a new computer.  That's the risk you take with older software.

A company called Winsoft was contracted to produce and sell the ME versions of adobe software.

To my knowledge adobe never sold ME or CE versions of their software, but that was handled by Winsoft.

So you would have to contact Winsoft to get CS3 ME. Id be surprised if they had a non activation version, so

you may have to settle for the standard/extended cs3 available from adobe.

https://winsoft-international.com/

Photoshop CC has all the ME functions built in so no more separate versions if you really need the cs3 me features.

As far as I know Adobe has not been selling licenses for CS3 for about a decade now, so where did you purchase it?