You will need to make sure that Installshield Express is building a 64bit Installer and not a 32bit Installer. There is information available at the link below:
Ultimately Installshield Express will automatically decide if it should build a 32bit or 64bit installer:
How InstallShield Determines Whether to Build a 64-Bit or 32-Bit Windows Installer Package
If one or both of the following conditions are true at build time, InstallShield creates a 64-bit Windows Installer package (in which x64 is specified for the Template Summary property):
• The Files view in the Express project contains one or more folders or files that are configured to be installed to CommonFiles64Folder, ProgramFiles64Folder, or System64Folder.
• The Registry view in the Express project contains one or more registry entries under the HKEY_LOCAL_MACHINE\SOFTWARE (64-Bit) node.
In addition, when InstallShield builds a 64-bit Windows Installer package, it marks the components that contain the files, folders, and registry entries in 64-bit locations as 64 bit.
If neither of the aforementioned conditions is true, InstallShield creates a 32-bit Windows Installer package (in which Intel is specified for the Template Summary property). In addition, none of the components in the package are marked as 64 bit. In this type of scenario, all of the files, folders, and registry entries are installed to 32-bit locations, even on 64-bit target systems.
