I am a big proponent of multiple monitors everywhere in the dental office. See the PC Mag article linked below for instructions on how to do it. Here is my office manager Jackie with two monitors at the front desk.
I’m going to assume that you have Microsoft Windows XP or Windows Vista. Given that, you’ll need a graphics card or graphics subsystem that supports multiple displays. Any video card manufactured in the past three years—even the budget cards—can do that. But take a minute to refer to your PC’s manual if your system has only integrated graphics hardware—that is, a graphics adapter that’s built into your system’s motherboard chipset. Some integrated graphics systems can handle more than one display, but others can’t.
The bottom line is that you need a graphics adapter with two physical connectors—either VGA or DVI—and two displays with appropriate connections. If you have a video card with two DVI ports, but one or both of your displays has only VGA connectors, you can obtain DVI-to-VGA adapter dongles.