If you Google the exact phrase, you will find forum threads from 2009, sketchy YouTube comments, and "keygen" download links. Here is the hard truth about those results.
The official eJay website still hosts demo versions of older titles. The demo of Hip Hop Ejay 5 will let you use the software for 60 minutes per session. It doesn't save your projects, but it lets you scratch the nostalgic itch without a serial key.
So, why are people searching for the today?
For a teenager in 2005, cracking open Ejay 5 meant you could sound like a Timbaland clone in ten minutes. For that reason, its serial number became as valuable as a guitar pick at a rock concert.
Bandlab is the spiritual successor to Ejay. You can take loops, remix them, and even collaborate with others. It is completely free and legitimate. It does not require a CD, a crack, or a serial number.