Which version of LabVIEW are you using? Is the DLL that's missing one that you you manually put in your project or one which you didn't recognize until an error came up?
If you build an installer which includes a DLL you made, you need to include that DLL as an additional file. See this link for how to organize and manage projects in LabVIEW 8.2. For adding items specifically, see the link which says "Adding Items to a Project".
Regards,
Craig D
Applications Engineer
National Instruments
