As it may happen to other peoples, I will answer my own question.
42 views without any idea about how to resolve my problem... Fine.
I have changed the way to ask the question by not mentioning Grimefighter and search on google : "PC won't start, blocked on black screen".
I have found many answers but one worked with me but needed a bit of work :
If you are also blocked on a black screen inviting you to go to the Bios but are unable to type any command because the screen is, like i have had, frozen, just do as following :
1) turn your pc off,
2) unplug it
3) wait for a minute or so
4) find on your motherboard the CMOS battery
5) when found, take it off (which can take a moment depending on the way it is set on your Card - I needed a bit of time before taking it off)
6) leave the battery aside for 5 minutes or so
7) unplug your RAM (I have read this step, just did it, but I am not sure it had any effect on the good working of this process)
8 ) after having waited, let's say 10 minutes, set the CMOS back on your motherboard, plug your RAM, re-close your PC and plug it back
9) Start your Pc, everything should come back to normal, maybe the Bios will invite you to reconfigure it, if you didn't make any change to it, just go forward and enjoy :-)
My solution was found on a french speaking website called "Comment ça marche" (
http://www.commentcamarche.net/forum/affich-3611061-mon-pc-ne-boot-plus-et-bios-inaccessible)
If it can help those of you who are still stuck with Grimefighter,
Bye,
Elrad