I need to change the Win 7 background

Hi - wonder if anyone can help...? Is there a way of changing the whole of Win 7 background to black without using a high contrast theme? You might think this a strange question but my partner is visually impaired and white or yellow text on a black background is so much easier to see. I know that this can be achieved using the high contrast setting but herein lies the problem. She uses a program from Dolphin Computer Access called Guide which is adapted for visually impaired users. If Win 7 is set to high contrast then anything she prints from Guide comes out as a solid black page (horrendous ink consumption) and will only print normally when HC is off. I can set the wallpaper to solid black but when using Windows Explorer for file management the background is white. This, and all the other windows, is what I want to set to black.....

Thanks for all the suggestions guys but I am a bit of a novice at this. If you look at the attached screenshot you will see that the desktop background is black (Thanks Andrew) but when I go into My Computer, Windows explorer or any program that needs to open another window they are white. I need a simple remedy that will make everything have a black background. My reasons for doing this is that my partner has a visual condition that sees white on black much, much better than black on white. Cannot use Windows high contrast - see original post so I am looking for an alternative...

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