Ubuntu 8.04 screen resolution limited with Nvidia Geforce2 MX-400
Installed Ubuntu 8.04 on an old unused white box. Install was uneventful, but resulting screen resolution cannot be increased beyond 800x600 (sometimes only 640x480). Am using a 17" LCD panel with 1280x1024 native resolution. 800x600 is just unacceptable. Have Googled problem and spent an entire day on this to no avail. Video card is Nvidia Geforce2 MX-400 with 64MB. Have tried all drivers mentioned in posts: nvidia, nv, nvidia-glx, nvidia-glx-legacy. No change, resolutions above 800x600 do not appear in Screen Resolution list. Editted xorg.conf many different ways adding Modes lines to Monitor and Device sections. Added vert/horiz sync range lines. No help. Tried running nvidia-settings, but it won't run complaining "Not using Nvidia X driver". Says to edit xorg.conf or run nvidia-xconfig. Installed and ran nvidia-xconfig, but no change. One suggestion was to rerun X configuration and chose screen resolution there. Tried that, but all it asked was questions about the keyboard and nothing about the video adapter or screen.
Installed and ran Ubuntu 6 with this video card and monitor with no problem (once I learned how to manually configure xorg.conf). But 8.04 seems to have regressed and no longer works with a Geforce2. I had first tried an old 3dfx Voodoo3 2000 and had the same problem. When I searched for instructions on video card problems, found info only for ATI, Nvidia, and Intel (implying others not supported by omission). So I switched to the Nvidia card.
What am I missing?