Calendar

Right click on the calendar above and choose "set as background"
"Set as Background" may be "Set as Wallpaper" on your machine

If the background doesn't fit properly right click on the desktop away
from any windows or icons and choose "properties", select the
"Desktop" tab and change the "Position" setting to "stretch", click OK.
("Desktop" and "Position" may be "Background" and "Display")

If the white text on your desktop icons don't have enough contrast, right
click on the desktop away from any windows or icons and choose
"properties", select the "Appearance" tab and click the "effects" button.
Ensure "Use the following method to smooth edges of screen fonts"
is ticked. Change from "Standard" to "Clear Type" and click OK.