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.
The Rundll and Rundll32 utility programs were originally designed only for
internal use at Microsoft.
This article from Microsoft's Knowledgebase offers a detailed description of what RUNDLL and RUNDLL32 do: Info: Windows Rundll and Rundll32 Interface (Q164787)
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
Safe
Microsoft.com