If you are searching for a "serial number" via search engines, you are likely encountering one of two scenarios:
Do not post it publicly (it will be deleted). Instead, submit it to the eJay Legacy Database via the Vintage Software Archive. Your key could help historians document one of techno’s most accessible starting points. serial+number+ejay+techno+4+reloaded+exclusive
You can often find original CD-ROMs on eBay or Amazon for a low price, which include a valid serial number inside the case. Modern (and Free) Alternatives If you are searching for a "serial number"