what video card is inside the machines, download the correct drivers and install them. That would do the trick.
Two ways to find out:
1. Have a look at the card itself. If no video card, but an on-board graphics (that's: on the motherboard) you'll may need to find the motherboard drivers.
2. Remove the video from Device Manager, reboot and see what the New Hardware wizard has to say. If it's an old card, it might be that the OS has a basic driver for it on the CD. This wouldn't harm as you can always install what you've got now.
If all else fails, buy a few second hand simple videocards (with driver CD or with enough identification), on ebay for example. So many people buying the hottest, latest card for the hottest, latest games they must be abundant.
Hope this helps.
Have found problems with Win98SE from the Schools computers I am envolved with;
On Three of their Computers I have found somehow we have lost the original setup with the Graphics!
At the moment all we only have is "16 colours and 2 colours" available and in "System Properties" it only shows one "Display Adaptor" " the "Standard PCI Graphics Adaptor [VGA}".
I feel at the moment the Graphics Chip has somehow collapsed and become non functional?
I am trying somehow to over come the cost problem!! I may yet have to ask the School to buy me new Graphics Cards???
 Also finding the program pages are to large for the monitor screen [just a few = EG, "Adobe Reader 6.01 = Preferences"].
Unable to pull up the bottom of their pages so to click on "OK" /"Cancel" Keys and they have no "Minimise" available on their/these pages and found you cannot "Drag" them smaller from the page corners!
Your advice would be appreciated!
Regards Colin Darby [Australia]