Windows Services - RUNDLL32.EXE

RunDLL and RunDLL32 are commonly found in the startup group and used to call functions directly within a special program library that may be shared by other programs. Frequently, they're used to initiate a power management program or a screen resolution manager. Common examples include:
RUNDLL32 IEDKCS32.DLL - installer service
RUNDLL32 TWEAKUI.CPL,TWEAKMEUP - Microsoft PowerToys
RUNDLL32.EXE NVIEW.DLL,NVIEWLOADHOOK - nVidia Graphics
RUNDLL32.EXE POWRPROF.DLL,LOADCURRENTPWRSCHEME - Power Mgmt

The Rundll and Rundll32 utility programs were originally designed only for internal use at Microsoft but are now included in all versions of Windows from Windows 95 through the Vista family of products.

This article from Microsoft's Knowledgebase offers a detailed description of what RUNDLL and RUNDLL32 do: Info: Windows Rundll and Rundll32 Interface (Q164787)

Fixes for common problems:
Frequently used programs not automatically added to the Start menu (Windows XP and Vista) - http://support.microsoft.com/kb/282066.

"RUNDLL32.EXE - Entry Point Not Found" Error Message When You Start Your Computer - http://support.microsoft.com/kb/330159.

"Rundll32.exe entry point not found" error message when you open My Computer System Properties or the System Configuration Utility - http://support.microsoft.com/kb/832323/.

Error Messages in Mmsystem.dll or Rundll32 - http://support.microsoft.com/kb/138835.

Microsoft Java Virtual Machine locks up Windows XP - http://support.microsoft.com/kb/555107.

You receive "Remote Access Connection Manager" and "Remote Assistance Prepare System Restore" error messages in Windows XP - http://support.microsoft.com/kb/829779.

Rundll32.exe is a perfectly safe and a required Microsoft file. But it should be noted that rundll32.exe may be overwritten by some viruses such as W32/SirCam@MM. You'll find more information at http://us.mcafee.com/virusInfo/default.asp?id=description&virus;_k=99141. And some viruses use "look-alike" filenames such as "rundl132.exe" where the second L is replaced by the number 1.

Safe

Microsoft.com