Replacing an Application with Another in Windows

I recently received an e-mail form someone asking if it is possible to change the Task Manager in Windows. They had another application that they would like to use, instead of the built-in Task Manager. It is very possible to change the Task Manager, since I use Proces Explorer and have set it so I can use that application instead of Task Manager.

While Process Explorer provides this ability, many applications that provide the same functionality may not allow a user to replace the Task Manager. In this post I will not only show you how you can easily do this, but also how you can do this for almost any application within Windows.

Execute One Application, Get Another

Before continuing, I should provide a warning. This post will explain a process that involves editing the Windows registry. You must always be careful when editing the Windows registry as bad things could happen if you change the wrong key or value. If you follow the steps outlined below, you shouldn’t have any problems.

With that out of the way, let’s move on. When I enabled the “Replace Task Manager” setting in Process Explorer, I was curious as to how that was accomplished. When I right-clicked the taskbar and then clicked “Task Manager”, Process Explorer appeared. The same happened when I pressed CTRL+AL+DEL and clicked the “Task Manager” button. What was changed to accomplish this?

After doing some research I found my answer. In the Windows registry there is a little known key that allows you to execute a command whenever a specific file is run. In the case with Process Explorer, whenever the “taskmgr.exe” file was run, the “procexp.exe” file was executed instead.

To change the Windows to launch another tool instead of the Task Manager, you could use the following steps:

1. Open the registry editor.
2. Navigate to the following key: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options.
3. Right-click on Image File Execution Options and then select New->Key.
4. With the new key name highlighted, type taskmgr.exe and press Enter.
5. Click the taskmgr.exe key and then right-click an empty area on the right side and select New->String Value.
6. Rename the new string value to Debugger and press Enter.
7. Double-click Debugger and then in the Value data field type in the full path to the file you would like to execute.
8. Click OK to save you changes.
9. Launch the Task Manager by one of the following methods:
   1. Right-click an empty are on the taskbar and select Task Manager.
   2. Press CTRL+AL+DEL and then click the Task Manager button.
   3. Click Start->Run or press the Windows Key+R and type taskmgr.exe.
10. When you run Task Manager, the application you typed into the registry will open instead.

You can replace other applications in the same manner. I have tried it with Notepad, although with at times mixed results. I have used it to prevent applications from running by using a dummy execuable, one that doesn’t do anything, or called “rundll32.exe” with no parameters, which also does nothing.