install.dll is not a Windows file. Despite the generic name, it is a private helper that a program's setup or uninstaller carries with it - every product has its own. When Windows says it is missing or could not be loaded, something happened to that one installer: a broken download, an antivirus quarantine, or a damaged temp folder. That is good news - the fix is local and quick.
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Delete the installer you have, download it again from the official site, right-click the new file, open Properties and press Unblock if the button is there, then run it as administrator. This clears the three most common causes at once: a corrupted download, a Windows block on the file, and missing permissions.
A dropped connection or a disk hiccup leaves the installer archive damaged - it starts, but cannot unpack its own helper files.
Security software sometimes pulls a single file out of an unpacking installer. The setup then reports exactly this: its DLL cannot be found or loaded.
Files from the internet carry a block mark. Some installers cannot load their own DLLs while blocked - the Unblock button in file Properties clears it.
Installers unpack into the temp folder. Leftovers from failed installs, a full disk or broken permissions there stop the unpacking halfway.
%temp% and press Enter.Do not do this: Never download install.dll from a "DLL download" site. Every product's install.dll is different despite the shared name - a random copy cannot work, and such sites are a well-known malware channel. The right copy always comes inside the official installer itself.
No. Unlike kernel32.dll or vcruntime140.dll, install.dll is not part of Windows. It is a helper that a specific program's setup carries inside itself, so SFC will not find or restore it. The fix is always about that installer: a clean re-download, unblocking, or a repair of the program it belongs to. For errors in real system DLLs, see the DLL file errors guide.
Because every product's install.dll is different - the name is generic but the contents are unique to that installer and version. A random copy cannot work, and DLL download sites are a well-known malware channel on top of that.
The program's uninstaller lost its own helper file. Reinstall the same program over itself first - that restores the uninstaller's files - then uninstall normally. If the installer is no longer available, Windows' built-in troubleshooter for installing and uninstalling programs can remove the leftovers.