Using Rundll32.exe in Windows

What is Rundll32.exe?

Dynamic Link Libraries (Dlls) are used by Windows operating systems, such as Windows XP and applications installed on it to perform various functions. Most of these functions are used internally and you don’t get to know about them. However, Windows comes equipped with Rundll32.exe, which is a command-line utility that you can use to invoke certain functions exported from DLLs. In this article, we will discuss how to use Rundl32.exe and go through a few examples.

Syntax to Use Rundll32.exe

The syntax to use Rundll32.exe is:

RUNDLL32.EXE <Dll_Name>,<Entry_Point> <Optional_Arguments>

The command should follow the following standards:

DLL_Name: Do not include spaces, commas, or quotation marks in the DLL name. If the DLL name consists of spaces, then you must use the 8.3 version or the short name of the DLL.

Entry_Point: Entry point is case sensitive, therefore, you must follow exact casing while adding this value. Also, remember that if the DLL file does not exist in the system folder then you may need to enter the full path for the DLL name.

Optional_Arguments: This part is used to specify any additional task that you want the command to perform. For instance, if you run the following command:

RUNDLL32.EXE SHELL32.DLL,Control_RunDLL desk.cpl,,0

This opens the Display Properties dialog box with the Desktop tab open. Now, you can change the value of the number at the end to specify the tab you want to open with the command.

Note: While running the command you must be sure to follow the exact syntax, otherwise, you may receive an error message.

Rundll32.exe Examples

Let’s now see a few examples of using the Rundll32.exe file. To run the commands discussed here, open Start > Run, enter the command in the ‘Open’ field and select ‘OK’.

Switch Mouse Buttons

To switch mouse buttons for a left-handed user, run the following command.

RUNDLL32.EXE USER32.DLL,SwapMouseButton

This command cannot be used to switch back to default settings, To switch back, you will have to go to Control Panel and open the Mouse Properties dialog box. However, you can directly open the Mouse Properties dialog box by running the command given below.

RUNDLL32.EXE SHELL32.dll,Control_RunDLL main.cpl @0,0

Clear Internet Explorer Title

Some ISPs and software programs modify the title of the Internet Explorer to include their brand name. You can remove this added information and clear the Internet Explorer title bar by running the following command.

RUNDLL32.EXE IEdkcs32.dll,Clear

View Printer Options

To view various print and printer setting related options available on your system, run the command given below.

RUNDLL32 PRINTUI.DLL,PrintUIEntry /?

Hibernate Your System

The power options of some computers—laptops and notebooks—enable you to hibernate them instead of performing a system shutdown. You can use this option when you are going to be away from your PC for a short time. To quickly hibernate your PC, run the command given below.

RUNDLL32.EXE PowrProf.dll,SetSuspendState

Rundll32.Exe Error Messages

Generally, rundll32.exe error messages are displayed when you accidentally download malicious software such as viruses, Trojans, spyware, and adware on your system. These malicious software programs are downloaded when you access dubious websites, open suspicious email attachments, and download uncertified freeware programs. Rundll32.exe errors can also be caused by incorrect software install/uninstall and a damaged registry.

To keep your PC free from rundll32.exe error messages, you must be a vigilant user and be very careful about what you access on the Internet, and what files you download on your system. You must follow correct install/uninstall procedures and use a registry cleaner program to regularly scan and repair the system registry.

Runndll32.exe is used to invoke functions exported from DLLs to perform various tasks. Although, an application may use Rundll32.exe to perform various functions, you can use it to perform a few functions manually. In other words, Rundll32.exe commands can be used as a shortcut to perform certain tasks that otherwise, would have required you to navigate through a number of dialog boxes and windows. To keep your PC free of rundll32.exe error messages, you must keep your antivirus software up-to-date and regularly run antivirus and registry cleaner scans on your system.