Why is Display Smaller than Monitor Screen?

[JudithWright]

PC Specs:

HP Z420 Workstation

CPU: Intel Xeon E5-2670

GPU: NVIDIA Quadro K600

RAM: 256GB AXIOM PC3-10600 DDR3-1333MHz ECC Registered CL9 240-Pin DIMM 1.35V Low Voltage Quad Rank Memory Module

Boot Drive: 128Gb Silicon Power 2.5" SSD

OS: Windows 10 Pro 64-bit

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Monitor Display is smaller than the screen size (with a black box around the Windows display).

I have downloaded every possible update from Windows update. Also, manually downloaded (and installed) Quadro Desktop Driver 410 from the NVIDIA website

Some of the other NVIDIA Driver Updates I have tried manually installing (i.e. 470) give me an error message : "nvidia installer cannot continue nvidia graphics driver not compatible version windows"

I have gone through the "standard fixes" like trying to change the screen resolution size in Windows - and none of these have worked.

I currently see a PC with similar specs for sale on Newegg, so I am not understanding why this setup is not working.

Why is the Display smaller than the Monitor screen?

How can this be fixed?

Also:

I uninstalled everything and borrowed an NVIDIA NVS 310 to see if it would work, and the display started to work in the same way (with the black square around the display).

But then, when I ran all of the standard Windows 10 updates, the display corrected - and works normally.

Why would the Hp Z420 work normally only with the NVS 310 but not with the K600?