Yes.
The process is the same as installing a second video card, but leaving the internal video display active in Windows and don't reduce the shared memory for video in Setup. The primary display will be determined based on the choice for "Init Display First" under the Integrated Peripherals menu in Setup. If this is set to AGP, then the integrated SiS video is the primary, If set to PCI, then your new adapter is the primary. Use the Display control from the Windows Control Panel to adjust the size, position, and color depth for the two monitors.

Installing a second video card:

DO NOT remove the Video Card drivers (The SIS video chipset will still be detected, and Windows will prompt you for the drivers if you delete them. Our system locked up as the drivers were reinstalled, because Windows tries to initialize the SIS video, and cannot, once the memory has been set to none.) Close all windows, use Start, Shut Down, Restart the computer.

• During startup, press Delete to enter Setup
• From the main menu, select Integrated Peripherals
• Change Init Display First to "PCI"
• Press Escape, Exit save changes
• Power the system Off
• Install the new card in an available PCI slot
• Connect the monitor to the new card and restart
• Press delete to enter Setup, and return to the Integrated Peripherals menu
• Change VGA Shared Memory Size to "none"
• Press Escape, and select "Save and Exit Setup" from the main menu

When Windows restarts, it should detect the new video card and prompt to load drivers. Follow the manufacturer's instructions for loading Windows 98 drivers or running their Setup program to install them.

Device manager should show the SIS video with an "!" next to it, indicating it could not initialize the card. This is normal, since the card has no video memory allocated. You can select the SIS video device and click on the properties button, then place a check mark to "Disable in this hardware profile."