Microsoft may have abandoned driver work for XP. It shows in your testing. Also I would never use an old webcam for pictures. Today I use my phone.
I have a "Microsoft lifecam HD-3000" web cam
I have uploaded 2 images using the same camera, the better quality image was taken on my win 10 laptop, but the poor image was taken on my win xp computer.
On my win xp machine; in the control panel-display-setting tab, the screen resolution is set to 1024 by 768 pixels and the color quality is set to Highest (32 bit). So should this not be enough?