What does rundll32.exe do?

[aclayborne]

What does rundll32.exe do and what type of dlls work with it. I have a SDK that requires me to register the dll's with this command:
("RUNDLL32.EXE xxxx.DLL,Install /NOUI", 1)
The OCX file associated with the dll won't run properly if I simply try to register the dlls.
Is there anyway to access the code in xxx.DLL so I can see what actually being done.

 

[SemperFiDownUnda]

RUNDLL32 and RUNDLL (only available on win9x and ME OSs) are designed to help test some DLLs. It provides the EXE that a DLL can link to and can be used to call exported functions. The DLLs have to be writen with RUNDLL in mind, ie they must be writen to support that functionality.