How to Factory Reset MID9042?

[5arid]

OK, I rooted my MID9042 by using this thread :
READ FIRST: Development Index and Root Utility
Now there is a Superuser icon in the apps menu!
Then I dumped these files : boot.img, bootloader.img, recovery.img, and system.tgz

Edit 1 :
I installed this file from sdcard by using Android system recovery <3e> :
9042_recovery_signed
This time when I push and hold Power and + , instead of "Android system recovery <3e>" I have "CWM-based Recovery v6.0.2.8 9042 by Vampirefo"

 

[tpaine]

Good work. Please post your system dump to the firmware request thread.

 

[5arid]

You know, I already used LiveSuit to install an img
So these files are not the original firmware dump of MID9042
Than again I can upload them if they are really useful