: Ensure the "bitness" matches your executable. Most legacy LabVIEW 8.5.1 applications are 32-bit and require the 32-bit Runtime , even on 64-bit Windows. Are you trying to run an existing legacy application on a newer computer, or are you looking to upgrade a project to the 2021 environment? LabVIEW and LabVIEW Run-Time Engine Compatibility - NI
National Instruments (NI) maintains an archive of legacy drivers. labview runtime engine 85 1 download 2021
If you're looking for alternative solutions or newer versions of the LabVIEW Runtime Engine, consider the following: : Ensure the "bitness" matches your executable