Where to (safely) get installer updates

Specifically, you might be searching for the "Windows Installer 50 download for Windows 10 64bit new."

: If you receive errors like "Windows Installer Service could not be accessed," you can fix it using the Command Prompt: Open Command Prompt as an administrator. Type msiexec /unreg and press Enter . Type msiexec /regserver and press Enter .

cannot be downloaded as a standalone redistributable package

Are you seeing a when trying to install a program? Install Windows Updates - Microsoft Support