Both of the aforementioned screen readers work with Windows 98 and Windows Millenium Edition. Jaws For Windows also has a Windows NT version. A flat-bed scanner. However, I don't recommend the cheap ones because they are slow and they don't last long. You get what you pay for.
Many older computers have the older uni-directional parallel port.
Scanner technology and models keep changing. An OCR program for blind use. The benefits of the Omni 1000 are better accuracy and it includes the Flex-Talk software speech synthesizer. Omni installs much quicker and easier than Openbook. These cost a lot more than OCR packages for sighted people such as Omni Page, due to them including the screen reader.