Google for a monitor display test pattern. If the display can be adj. you can try with that as a reference, otherwise, you may have incompatible setup in some way. I suggest you also check the bios doesn't have some video feature, thus disable if so found. Older systems and components can be trying as you maybe finding out why it was sold, good or bad.
I was given an older Gateway e 4200 computer. I had to buy a video card since the computer didn't have one in it. I bought the card off an online auction site. At the same time I purchaced 256 mb pc 100 ram card. The video card I purchaced is a ATI radeon 7000 64mb pci card. I downloaded the drivers from ati.com and since had problems with vertical line across the screen. I tried the card in a newer pc and it seemed to work fine with no lines, using the same monitor. The os is windows 98 for now and the computer has just an 8.4 gb hdd, which I plan to upgrade soon if I get the vertical line problem fixed.