The Windows 7 OS has made many improvements over its predecessors (namely Windows Vista), one of which includes transcoded wallpaper themes. This means that when you save an image as your desktop background, Windows 7 will automatically convert it to a .jpg file, regardless of its original format. During this process, however, files can occasionally be corrupted, or settings can be altered. If you are unable to change your desktop background, then there are a few possible solutions to your problem.
Method 1
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Step 1
Click the "Start" icon, located at the bottom right-hand corner of the screen.
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Step 2
Select "Control Panel" to open a new window. Click the "Ease of Access" icon, followed by the "Ease of Access Center" icon, on the following page.
Step 3
Click the link that says "Make the computer easier to use." This will open a new page.
Step 4
Scroll down until you see the option that says "Remove background images." Make sure this option is unchecked. If it is not, uncheck it.
Step 5
Click the "OK" button twice. Wait momentarily while your settings are changed. Exit out of the "Ease of Access Center" window.
Step 6
Change the background image now. If it still does not work, try the following method.
Method 2
Step 1
Click the "Start" button located at the bottom right-hand corner of the computer screen.
Step 2
Select "Control Panel" to open a new window. Type "troubleshooter" into the search box located in the upper right-hand corner of the window.
Step 3
Click the link that says "Troubleshooting", to be directed to a new screen.
Step 4
Click the link that says "Display Aero desktop effects" under the "Appearance and Personalization" section.
Step 5
Click the "Next" button and wait momentarily while the application searches for errors regarding your desktop. Follow the on-screen prompts to resolve any errors. Try to change your background when you are finished. If this method does not work, try the following method.
Method 3
Step 1
Click the "Start" button located at the bottom right-hand corner of the computer screen.
Step 2
Copy and paste the following code into the search bar, then press "enter" on your keyboard. %USERPROFILE%\AppData\Roaming\Microsoft\Windows\Themes\
Step 3
Right-click the file entitled "Transcoded Wallpaper," and then select "Rename." Change the name to "transcodedwallpaper.old" instead of "transcodedwallpaper.jpg" (you really only need to change the last three letters). Click "Yes" to confirm this action when a pop-up dialog box appears.
Step 4
Double-click the "slideshow.ini" file. This should automatically open in Notepad. Erase all text that appears in this file (if there is any), and then click "File," followed by "Save" in Notepad.
Step 5
Exit Notepad and Windows Explorer. Change your background image. If this method still does not work, then you may need to upgrade your Windows 7 to a version other than "Windows 7 Starter" or "Windows 7 Home Basic."