I have an older Viewsonic VS12264 LCD monitor. It's been a great little unit, which I used to connect to via DVI.

However I have needed to change to HDMI. I now have a few different PC's in my office which I share with the same screen, keyboard and mouse, so I'm using a HDMI/USB KVM device.

The VGA Card in my main PC has both a DVI and HDMI port. However I can't plug the HDMI cable direct into the HDMI port - I think the PC case actually prevents the cable from seating 100%. So I purchased an adapter (something like this:  https://www.jaycar.co.nz/hdmi-socket-to-dvi-d-plug-adaptor/p/PA3644) and my HDMI cable plugs fully/properly into that. 

However, for the life of me, I can get my Windows desktop to "sit properly" in the monitor window. There is a small portion of the Desktop, which sits outside the physical window of the monitor.  The monitor settings are useless and don't offer much value (as far as I can tell) and I can't seem to find a way to adjust the desktop, either through Windows Settings or the VGA software.

Any ideas?