Dell Precision M6800: stuck to PXE boot, can't access BIOS

Hello, I have this problem : link

What happen : when i boot my computer, the computer try to boot into PXE mode which doesn't work, when i try to access bios, i cant, because PXE show up first.

I can see on the screen : 

"Initializing Intel(R) Boot Agent GE v1.5.38.01

PXE 2.1 Build 092 (WfM 2.0)"

What was i doing before this happen : Trying to install rhel 7 (I modified different bios parameters and also the grub parameters)

What did I try to fix this problem :

- remove all hard drives from the computer

- try to boot with only one hard drive

- try to boot when another hard drive which have windows 7 installed on it (following the advice on the other topic)

- try to boot from a DVD (linux distro)

- unplug the WLAN 

- unplug the internal battery

nothing worked... i still can't boot my computer