This problem has nothing to do with PixInsight. The file you are referring to is a system component that should be provided by any clean and reasonably updated Windows installation, at least since 2015.
Research indicates that this should be provided by the install software. Could it possibly be left out of the version ?
Not at all. As noted, this file is a system component, so it should be provided by your operating system. These critical components must be kept up-to-date and synchronized with the rest of the system, and this is the sole responsibility of the operating system.
Besides this, please note that Windows 7 and Windows 8 are not supported by current versions of PixInsight.
The only Windows version supported by PixInsight is Windows 10.