Can't duplicate display on HDMI and VGA outputs (ATI Radeon HD4200)

I'm running Windows 10 Pro x64 on my HTPC based on a Asus M4A785D-M PRO board (with an onboard ATI Radeon HD4200). I have the HDMI output connected to my TV. I want to pass a 2nd (duplicate) video feed to another (analog) display using the VGA port. None of the options in the Windows "Project" settings seem to work as I want however. If I select "Duplicate", which seems to be what I want in theory, the HDMI output goes blank while the VGA output displays the desktop. If I select "Extend" I can see the main desktop on the HDMI output, but the VGA output shows a different display (i.e. an extended desktop).Is there any way of getting the same desktop to be displayed via both the HDMI and VGA outputs?

alphanumeric said:

I do believe, in duplicate, it defaults to the lowest resolution of the two monitors. And then tries to display that resolution on both. This causes one of the monitors to be at the wrong resolution. Some will display anyway and some won't, they are out of rage. I'm guessing this is your issue, just a guess though. I run triple displays but never in Duplicate Mode. I'm either in Extend or PC only.
To make the best use of the Duplicate mode, both displays should be the same resolution.

I suspected that it might be something like that. Is there any kind of software or driver workaround for this?

alphanumeric said:

There are likely third party utilities to get around it. A quick google search found this, https://www.displayfusion.com/ I'm sure there are others. You'll have to read the details to see if it will suit your needs.

Many thanks for the link. I've contacted them to see if the DisplayFusion product can help with this.

alphanumeric said:

It's a shame, in this day and age, that Windows can't do that natively. Hopefully that works for you.

Sadly they've replied to tell me that their software can't help :0(

Thanks - yes I think a splitter is the simplest way to go. I'll scout around on eBay...