MONITOR DOESN’T WORKS PROPERLY

Every time I put a video card (trident 9440) in my computer and then I try to configure it to use 256 collors or more, it becomes to be trembleling, and no image appears in one of my computers. What is happening? I tried to atualize the drivers and ?t doesn’t solve. The monitor is I use in this micro is SVGA and it’s oldier. What can I do???