When I try to install any recent version of Ubuntu, the screen shows some green and purple mess (like analog TVs when thers no signal). Then, a black screen. I guess it keeps booting in live/install mode. But I can't see it. I tried installing from CD and USB, I tryed changing some BIOS settings... I installed older versions, like 8.04, and it worked, but after updating the system, it crashes again. That's why I discovered that upgrading Nvidia drivers, made system show a black screen again. After that, I unplugged the Nvidia card and installed 12.04 with onboard card. It worked perfectly. Then, I plugged Nvidia again and system booted, but only showing that black screen again. I keep working with onboard card, so far... The nVidia is a GeForce 8500GT.