Frantz,
Did you install it using Softaculous autoinstaller? If yes, then your EPESI will be automatically updated and backed up - if you selected this option. However it will not be stored in your EPESI directory.
If you find this file: epesi-1.5.5-20140113.zip it means most likely that this file was downloaded and placed there by someone who has access to this directory.
The file needs to be decompressed and the entire content copied into the directory where your EPESI is installed, overwriting existing files. When you open EPESI the next time an upgrade will be performed automatically. But files from the .zip file need to be extracted first. Just downloading the file will not update your EPESI application.
See this for more info: http://www.epesi.org/Installation
You can check which version you run: Menu-> Support -> About
For example: EPESI version 1.5.6 rev20140305
Also - if you are not sure if the update was done correctly you can download it again, override all files and check your version - there is no risk to run the update again.
