ArcadeVGA is a video card that allows people to drive a lower bandwidth signal than what is typically supported by modern PC monitors. One of the last PC monitors to support this lower (15Khz) signal was the NEC MultiSync3D which was popular with Amiga users at the time it came out.
Most modern PC's consider 31Khz or 640x480 to be a more common lowest common denominator for expected low resolution support for a PC monitor. Because of this, modern graphics cards typically disable this mode to prevent users from being concerned that the video card might not work at low resolutions (in reality it would be the monitor, not the video card that wouldn't be working).
Using linux or hacking the driver, you can eliminate the need for such hardware. However, at the time of this writing, it's not generally know how to run in the lower resolution modes in windows.