I recently was trying to install Ubuntu on an machine for nefew and no matter what I tried I could not get the resolution to go above 800 x 600. I was very frustrated until I found the solution listed below.

But first, I will tell you about the whole ordeal. I started out by trying to use an Ubuntu 7.10 Live CD for the installaiton. The Live CD boot up just fine but resolution was only set 800 x 600 and when I tried to increase it by going to Preferences->Resolution I could only choose from 800 x 600 or 640 x 480. The problem with this is that when you launch the installer you can not see the buttons you need to navigate through or make selections during the installation process. (They are off the screen at the bottom.)

So, not knowing whether on not this might work, I ran dpkg-reconfigure xserver-xorg, verified that my video card, monitor, and screen resolutions were identified / setup correctly and then I logged out an logged back it (still using the Live CD). But I still could not get the resolution to go above 800 x 600. I even opened up the xorg.conf file and verified that everything was correct there. (The default resolution was being shown as 1024 x 768 in the xorg.conf file.)

So, I went the route of using the Ubuntu 7.10 Alternative CD to install Ubuntu. Everything went fine, but again I could not get the resolution to go above 800 x 600.

So, next, just for kicks I thought I'd try to install Debian 4.0 and see if it did any better. But, again, the same results. Then I came across a postingon the Ubuntu forums about people having this very same issue with nVidia GeForce2 MX400 and MX420 video cards that solved my problem.

The solution to the problem is to add the following to both the device and monitor sections of your xorg.conf file:

Option "UseEDID" "False"

I have put the relevant secotions of my new xorg.conf file below so that you can see where I put Option "UseEDID" "False".

 Section "Device"
        Identifier      "Matrox Graphics, Inc. MGA 2064W [Millennium]"
        Driver          "mga"
        BusID           "PCI:1:0:0"
        Option          "UseEdid" "False"
EndSection

Section "Monitor"
        Identifier      "EN-775e"
        Option          "DPMS"
        Option          "UseEdid" "False"
        HorizSync       30-70
        VertRefresh     50-160
EndSection

http://www.computerhope.com/help/video.htm