If you aren't sure if it's already installed, check the following system paths: LabVIEW Runtime Download - NI - National Instruments
Version 8.5.1 was released around 2008. It is officially supported on Windows XP, Vista, and Windows 7 labview runtime engine 8.5.1 download
Navigate to the NI "Drivers and Downloads" section. Search for "LabVIEW Runtime" and use the version filter to select 8.5.1. You will likely need an active NI user account to complete the download. If you aren't sure if it's already installed,
If you need it, use VIPM or contact NI with an active support contract. For personal or legacy system use, consider running a VM with Windows XP and LabVIEW 8.5.1 dev environment (if you have a license) then building a standalone installer that includes the runtime. labview runtime engine 8.5.1 download