The best place that has given an all-round answer for it, for all operating systems (since you don't specify which you have) is at: http://www.winguides.com/registry/display.php/791 It's a little bit technical, so good luck!
Without creating a all new theme for windows, you cant.
To change the background (or wallpaper) on a Windows Vista system you must first able yourself to change the desktop background. Then you can access it by clicking the Start button and clicking on the control button and searching for "appearance and personalization".
Start button/Windows button/Windows Key and then click where it says (My)Computer
In a windows computer the start button is the button in the far left bottom corner of your main screen or desktop, in older versions of windows it had start written in it now with vista you will see an "orb" (a round button with the windows symbol in it) which says "start" when you hover over it.
There is no Start button per se. Finder is the equilivant of Start on a Windows PC.
Search it in your start button.
The launch button for Windows is the Start button on the bottom left corner.
Why is this categorized in mens clothing? Also my Windows 8 start button is not an acorn so idk.
How do you change name of Start Menu in Windows
The control/command button is next to Windows' start or alt.
You don't. The only way to change the base language in Windows (start button, menus etc) is to reinstall windows with a disk in the language you require.
Press the power button