Is it possible to install SSD as a secondary drive in a Lenovo thinkpad e420s? It does not have a typical eject system. It is visible here 
SSD as a secondary drive in a Lenovo thinkpad e420s?
Beka
No it is not possible the DVD drive is non removable
David
No, as laptops have gotten smaller and smaller, the chances of fitting two hard drives in there are diminishing. What you can do is buy an aftermarket SSD or HDD or Hybrid drive, and replace your current drive with it. The slot insertion point is for an optical drive (CD, DVD, and/or Blu-Ray). You can't put a hard drive in place of the DVD drive.
You can check the datasheet about your system yourself, down below in the Source section.
Yousuf Khan
After doing some research I found that the E420s can be equipped with an mSATA SSD drive and has a special slot for it under a keyboard, in the center. This is cool, you can have a smaller mSATA as a boot drive and keep your data one a regular HDD
Beka