Following Up on Dual-Monitor Expansion

Before I get started with your questions, I want to pass along a comment I received regarding the tip "Dual-Monitor Image Expansion in Win2K," August 2001, InstantDoc ID 21014. In that tip, a reader asks why a coworker's Windows 98 Second Edition (Win98SE) laptop supports dual-monitor expansion, whereas the reader's Windows 2000 Professional system doesn't. (Both systems sport ATI Technologies' RAGE MOBILITY-M1 AGP video card.) In my answer, I explain that Win2K supports such expansion only when you attach a separate video card to each monitor.

Another reader recently wrote me with a second explanation for the problem. Apparently, the RAGE MOBILITY-M1 chipset supports a VGA-specific feature called dual head. Dual-head support lets you expand your desktop across your laptop's LCD screen and a connected, external CRT monitor—and requires only one video card. Windows XP, Windows Me, and Windows 9x support dual head, but Win2K doesn't. Furthermore, Microsoft-supplied video drivers don't support the feature, so even when your laptop's OS supports dual head, you must rely on your video-card manufacturer's display driver if you want to accomplish this type of monitor expansion.