In my Device Manager, I see several monitors listed even though I only have one or two monitors
This is normal behavior. NVIDIA GPU's allow a user to connect an external monitor while the computer is turned on. Microsoft Windows by default enumerates each display head at Windows startup only and therefore the NVIDIA Forceware display drivers create a display for every possible display output. For example, if the graphics card has a DVI-I port, the DVI-I can either send out a digital DVI signal or an analog VGA signal using a DVI to VGA adaptor. Therefore the display drivers reports two displays on this head even though there may only be one or no monitors attached to it.