1. How do I change my desktop wallpaper in Windows XP?
Find a new wallpaper you like and click on the green button to download the resolution you want (e.g. 1600x1200). A new window will popup with the full image.
Right-click on the image and select "Set as Background" from the popup menu.
2. How do I change my desktop wallpaper in Mac OS X?
Start by downloading a new wallpaper to your Desktop. Put this file in the "Pictures" folder inside your Home Directory.
Now open up the "Desktops & Screen Saver" preference pane in the System Preferences.
Next, click on the "Pictures Folder" item from the list. In the browse pane you should now see the desktop wallpaper you just put into your Pictures folder. Click on it and your desktop will immediately change to the new one!
3. How do I change my desktop wallpaper in Linux (KDE)?
Find a new wallpaper you like and click on the green button to download the resolution you want (e.g. 1600x1200). A new window will popup with the full image.
Right-click on the image and select "Save image as..." from the popup menu. Save the file to a convenient location on your hard disk. Next, minimize all your windows so that you can see your desktop workspace. Right-click on the desktop and select "Configure Desktop..." from the popup menu.
In the System Settings module that appears, select the "Background" icon from the left-hand side of the window, then click on the "Wallpaper" tab to your right. Finally, click on the "Browse..." button and navigate to the wallpaper you just downloaded. When you are done, click the "Apply" button to make your changes.
4. What if you don't have wallpapers in my display's exact resolution?
Select a wallpaper which is larger than your monitor's resolution and set your operating system to scale the image to fit. For the best results, make sure that you select an image with the appropriate aspect ratio so that it is not distorted or cropped.
For instance, if your display is running at 1024x768, you would select the 1280x960 resolution. It is larger, but has the same aspect ratio (1024/768=1.33 and 1280/960=1.33). Choosing a smaller resolution is not optimal because the image will become blurry or pixelated (jagged) when stretched to cover your entire screen.