For no apparent reason my computer has lost the ability to display desktop images. Upon opening the Display control panel and the “Desktop” tab, the browse button and the image selection box are all disabled, preventing the selection of desktop images. How can I fix this problem such that I can set the desktop image? The computer is running Windows XP Home Edition.

Windows allows certain permissions to be assigned through a system called “policies”. For example, an organization may wish to prevent users on a network from changing the desktop wallpaper (this is particularly useful in settings such as schools and universities where the administrators wish to keep a consistent environment for all users). Policies contain such settings and allow multiple settings to be packaged up into the one unit and then deployed onto the network. We use the term “policies” to generically describe the process, but if you want to talk Windows-specific this is normally referred to as a Group Policy (as policies can be assigned to different groups of users).

This is relevant to your situation because it seems that a policy has been applied to the computer preventing you from changing the desktop wallpaper settings. In many cases this is because spyware or other malware has infected the computer and then implements its own wallpaper. It then sets a policy so that you no longer have control over the wallpaper setting. So, before commencing the restorative procedure to fix the problem you should scan your computer for viruses and any malware. This is necessary because if we fix the problem and your computer is still infected, it is likely the infection will simply reinstate the problem. If you do not have any antivirus software on the computer now would be a good time to consider getting protected. My recommendation for antivirus software is ESET NOD32, as in my experience NOD32 has a very small footprint and does not hog system resources (which is the problem with many other antivirus products). NOD32 can be purchased from eset.com.au. If you would like a free solution then you could investigate AVG Antivirus Free which is downloadable from free.avg.com. Regarding software to scan your computer for malware I have found that the free solutions are actually the best. Download, install and then scan your computer using Ad-Aware Free (www.lavasoft.de), Spybot Search & Destroy (www.safer-networking.org), and Windows Defender (www.microsoft.com/downloads). Between these three utilities most threats on your computer should be detected and removed.

The policy settings are contained in the Windows registry so we will need to delve into the registry to undo this policy so that you can change the desktop wallpaper. Go to the “Start” menu > “Run” and type “regedit” (without the quotes) and click OK. In the Registry Editor window that appears, navigate to the following registry key (or folder, as they are represented by little folder icons in the registry editor): HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies. Expand “policies” and you should see a list of various other registry keys (folders). Check whether one of these keys has the name “ActiveDesktop”. If you do see a key with this name, select the key (if you don’t see this key do not worry, as we have a procedure later on should this be the case). In the right-hand pane you should see a list of settings (known as values) for the ActiveDesktop registry key. Check whether there is a value named “NoChangingWallPaper”. If so, double-click on this value and make sure it has been set to 0. If there is no “NoChangingWallPaper” value you will need to create the value and assign it 0. To do this, right-click on the “ActiveDesktop” key and select “New” > “DWORD Value”. Name the value “NoChangingWallPaper” (without the quotes) and then double-click on the value and set it to 0. Once this has been done, close the Registry Editor and then check whether you are able to change the desktop wallpaper. If the change does not take effect immediately you may need to restart the computer.

The above procedure assumed that you had the ActiveDesktop registry key. If you do not see a key with this name you will need to create the key by right-clicking on “policies” then “New” > “Key” and name this key “ActiveDesktop”. Once this has been done follow the procedure that was outlined previously. Be aware, since the ActiveDesktop registry key did not exist this means that the NoChangingWallPaper value will not exist (as this is a value within the ActiveDesktop key). As such, you will need to create this value and then assign it to be 0 as per the instructions above.

Should you find that the problem continues after changing the relevant registry keys, and you have restarted the computer, you may need to do an additional modification in a different part of the Windows registry. The portion of the registry which you just modified is HKEY_LOCAL_MACHINE which handles computer-based policies and settings. You will notice that there is another portion of the registry called HKEY_CURRENT_USER. As the name implies, this handles user-specific settings for the current user. Follow the same procedure as for HKEY_LOCAL_MACHINE but instead complete the procedure under the HKEY_CURRENT_USER\Software\Microsoft\ Windows\CurrentVersion\Policies registry key.