How to find out which installer package a given exe/dll belongs to

It appears like there might be a way after all! I recently discovered registry entries for files installed by Windows Installers under the following subtree:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Installer\UserData

I wrote a small Python script to lookup the installer for a file using the information stored there:

> python windows-installer-file-search.py opus.dll
File: C:\Program Files (x86)\Mumble\opus.dll
Product: Mumble 1.2.13
Install user: S-1-5-18
Cached installer: C:\Windows\Installer\2f6b072.msi

It is available here: https://github.com/Zero3/windows-installer-file-search

If you are okay with just finding plausible needles in the haystack, this quick and dirty abuse of 7-Zip will work:

7z.exe l -an -air!C:\Windows\Installer\*.msi > needlelist.txt

Then open needlelist.txt in any text editor, search for needlename.dll and you will find the corresponding .msi package in the listings generated by 7-Zip.

(Note: This method is 'dirty' because it just tells you which .msi packages that contains a file named needlename.dll. But it is probably fine for most use cases.)