What you have is a "Fixed mode" monitor. Modern monitors (Multi-mode or MultiSync) allow for multiple horizontal and vertical frequencies: That's why you can change from 640x480 to 1024x768 ... A fixed mode monitor only operates at specific horizontal and vertical frequencys. To operate a fixed mode monitor, one needs a video card that has its BIOS locked on just the frequency of that specific monitor.
Just to clarify, some fixed mode monitors will actually operate at several different resolutions. However, to get those resolutions, the video card still has to output at very specific frequencies. A little off and it won't be able to sync.
If you look at the specifications of a modern monitor it will say something like Horizontal frequeny 30-100KHz, and a vertical Frequency of 50-120Hz. While A fixed frequency monitor will be 640x480: horizontal 30.2KHz, Vertical 60Hz; 1024x768: Horizontal 60.4KHz and Vertical 60.2Hz
The reason modern multi mode monitors work on the PS/2 is because they are flexible in the frequency's they receive. So they can adapt to the specific frequencies that the PS/2 is supplying.
So, basicly you can't use the monitors in a Windows application without buying a speciality video card programed for that specific monitor. However, If I remember correctly, some multiSync video cards running in Linux allow driver modification to force the video card into fixed mode (You would have to modify a text file supplying the frequencies).