Windows 98/Me and Windows 2000/XP include a video display feature that Macintosh systems have had for years: the capability to use multiple monitors on one system. Windows 98/Me support up to nine monitors (and video adapters), each of which can provide a different view of the desktop.

Windows 2000 and Windows XP support up to ten monitors and video adapters. When you configure a Windows 98/Me or Windows 2000/XP system to use multiple monitors, the operating system creates a virtual desktop—that is, a display that exists in video memory that can be larger than the image actually displayed on a single monitor.

You use the multiple monitors to display various portions of the virtual desktop, enabling you to place the windows for different applications on separate monitors and move them around at will. Unless you use multiple-head video cards, each monitor you connect to the system requires its own video adapter.

So, unless you have nine bus slots free, the prospects of seeing a nine-screen Windows display are slim, for now. However, even two monitors can be a boon to computing productivity. On a multimonitor Windows 98/Me system, one display is always considered to be the primary display.

The primary display can use any PCI or AGP VGA video adapter that uses a Windows 98/Me minidriver with a linear frame buffer and a packed (nonplanar) format, meaning that most of the brand-name adapters sold today are eligible. Additional monitors are called secondaries and are much more limited in their hardware support.

To install support for multiple monitors, be sure you have only one adapter installed first; then reboot the system, and install each additional adapter one at a time. For more information about multiple-monitor support for Windows 98/Me, including a list of supported adapters, see the Microsoft Knowledge Base article #Q182708.

It's important that the computer correctly identifies which one of the video adapters is the primary one. This is a function of the system BIOS, and if the BIOS on your computer does not let you select which device should be the primary VGA display, it decides based on the order of the PCI slots in the machine.

You should, therefore, install the primary adapter in the highest-priority PCI slot. In some cases, an AGP adapter might be considered secondary to a PCI adapter. Depending on the BIOS used by your system, you might need to check in various places for the option to select the primary VGA display.

For example, the Award BIOS used by the ASUS A7V133 motherboard for Socket A processors lists this option, which it calls Primary VGA BIOS, in the Boot menu. In contrast, the Phoenix BIOS used by the Intel DB815-EEA motherboard lists this option, which it calls Default Primary Video Adapter, in the Video Configuration menu.

After the hardware is in place, you can configure the display for each monitor from the Display control panel's Settings page. The primary display is always fixed in the upper-left corner of the virtual desktop, but you can move the secondary displays to view any area of the desktop you like.

You can also set the screen resolution and color depth for each display individually. For more information about configuring multiple-monitor support in Windows 98/Me, see Microsoft Knowledge Base article #Q179602. The multiple-monitor support included with Windows 2000 and Windows XP is somewhat different from that of Windows 98/Me.

These versions of Windows support ten monitors, rather than nine as with Windows 98/Me. In addition, because Windows 2000 and XP use different display drivers than Windows 98/Me, some configurations that work with 98/Me might not work with Windows 2000/XP.

For more information about configuring multiple-monitor support in Windows 2000, see Microsoft Knowledge Base article #Q238886. For details of the display cards compatible with Windows XP in multiple-display modes, see Microsoft Knowledge Base article #Q307397.

Windows XP also supports DualView, an enhancement to Windows 2000's multiple-monitor support. DualView supports the increasing number of dual-head video cards as well as notebook computers connected to external displays. With systems supporting DualView, the first video port is automatically assigned to the primary monitor. On a notebook computer, the primary display is the built-in LCD display.

Even if your BIOS enables you to specify the primary video card and you use video cards that are listed as compatible, determining exactly which display cards will work successfully in a multimonitor configuration can be difficult.

Microsoft provides a list of compatible display cards in the Hcl.txt file located on the Windows 2000 CD-ROM, but this list does not contain the latest video cards and chipsets from NVIDIA, ATI, or other companies, nor does it take into account changes in supported chipsets caused by improved drivers. Unfortunately, the online version of the Microsoft Windows Hardware Quality Labs Hardware Compatibility List doesn't list information about multiple-monitor support for any version of Windows.

Consequently, you should check with your video card or chipset maker for the latest information on Windows 2000 or Windows XP and multiple-monitor support issues.

Because new chipsets, updated drivers, and combinations of display adapters are a continuous issue for multiple-monitor support, I recommend the following online resources:

• Home of the UltraMon multiple-monitor support enhancement program and an extensive database of user-supplied multiple-monitor configurations for Windows 98/Me, Windows 2000/XP, and Linux

• Digitalroom.net (click Tech Articles and then Multiple Monitor Guide). Excellent tips on multiple-monitor setups and links to other resources

Multiple-monitor support can be enabled through either of the following:

• Installation of a separate AGP or PCI graphics card for each monitor you want to use

• Installation of a single AGP or PCI graphics card that can support two or more monitors

A card that supports multiple monitors (also called a multiple-head or dual-head card) saves slots inside your system.

Most recent video cards with multiple-monitor support feature a 15-pin analog VGA connector for CRTs, a DVI-I digital/analog connector for digital LCD panels, and a TV-out connector for S-video or composite output to TVs and VCRs. Thus, you can connect any of the following to these cards:

• One analog LCD or CRT display and one digital LCD display

• Two analog LCD or CRT displays (when the DVI-I–to–VGA adapter is used)

• One analog LCD or CRT display and one TV

• One digital LCD display and one TV