Aspire 6920g doesn't boot after bios flash failed

Moved in the dedicated thread. If an admin can delete this thread, thanks.

Salutation to the forum's members. Excuse my poor english, I am french.

I recently tried to flash the bios of my Acer 6920G laptop because my 9500M GS Graphic Card was misfunctioning and I bought a 9600M GS new MXM card, normally compatible, to replace it. Because the new card was not recognized (black screen), I tried to flash the 1.10 bios with a 1.14 version, on windows. I didn't know it was risky to use winphlash with resident softs opened (antivirus and others), and the flash failed.

I now have a corrupted bios, but I am not able to reboot in a crisis mod (with a Crisis Recovery Disk on CD or USB Drive), even with the Fn + Esc combination.

The point is now the laptop automatically powers on when plugged (the fan is launched), without pressing the power button, and shut down after 2 seconds. Same problem if I try with the battery. And no way to restart it after.
It seems I can't access to any recovery mod for I am not able to power on the computer more than 2 seconds. I unplugged the CMOS battery during 12 hours, but no result (anyway the bios is corrupted). The only thing I didn't tried is to use an external USB floppy Disk (I have to buy one), but I fear it wouldn't change anything as long as I can't power on the laptop.

I'm working on this problem for dozens of hours to fix it, and your help and advices would be greatly appreciated.

Thanks in Advance,

Marvelus