To register a DLL with a command line change to the directory where your DLL is and run:
regsvr32 mydll.dll
Please note, however, that if you copy that DLL into C:\Windows\System , Windows will register the DLL automatically.

You can also make a DLL self-register within WPS like this:
While in Installation Expert in Feature Details section
-Select Files and browse for the DLL.
-Right-click on it and select Details
-Click on the Self-Registration tab
-Select Unordered

This will work and make for a smaller MSI than registering the DLL
during SetupCapture but looking up the SelfReg table in the
SDK (click
)
it says that it is not Strongly not
recommended:
The SDK then proceed giving 6+ examples of why not to use Self-registration.
