"Dualhead cards and true multi-monitor support on Windows 2000
Due to a limitation in Windows 2000, dualhead cards that use a single chipset to drive both monitors require special workarounds in the driver to be properly recognized by the system. If these workarounds are not implemented, Windows 2000 sees a single large monitor instead of two.
This causes the following problems:
using different resolutions for each monitor is not possible
windows are maximized to the desktop instead of the monitor they are on, and dialog boxes appear centered on the desktop, split across monitors. Software included with the card may be used to work around these problems though
taskbar is extended across both monitors instead of only a single one
multi-monitor software will not work properly
All major video card/chipset manufacturers do now have Windows 2000 drivers with full multi-monitor support.
Appian added support for their Hurricane cards, most likely also for other RADEON VE-based cards.
ATI has added support for the RADEON 9xxx cards, but not for earlier cards. See this forum thread for more information.
Matrox has supported this for a long time, when installing the drivers, make sure to enable support for independent displays.