pb Nvidia Geforce 6200 Debian testing

Hello,

I've got an Acer Aspire E351 with a graphic card Nvidia Geforce 6200.
I installed the last testing Debian in 64 bits.

I've got problem with the display. It looks like the screen is divided
by 4. The all parts haven't the same size but the up left part displays
the same thing the down right part and the up right part displays the
same thing the down left part.
I've got the problem in X and in the console mode.

I tried with Live Ubuntu, same pb.

I tried with Trinity rescue kit, no pb. It must use a specific mode :
vesa, framebuffer, ... I don't know, I'm quite lost with all this stuff.

I took a look at /var/log/Xorg.0.log but except this :
AIGLX error: dlopen of /usr/lib/dri/nouveau_dri.so failed ....
I haven't seen anything.

Finally, i wanted to see /etc/init.d/xorg.conf but there's no more this
file.

At first, the computer comes from a friend who had Windows and quite
suddenly he had this problem on XP. Now he bought a laptop and gave me
this one to retrieve RAM or something else.
At the beginning i thought about a Windows pb, so i launched antivirus,
cleaning, etc. I removed dust inside, etc., nothing.

Is it possible that's an hardware problem triggered only with specific
video modes ?
What would you advise ?

In advance, thank you for your help.