Win95 “Plugin” & “Library” Error Message

I Have a system which I am trying to update the software on. When I go to download a update from Microsoft or ZDNET intermittently the machine gives me an error message saying need “Plugin” or “Library File is Missing”. It doesn’t tell me exactly what plugin or libray file. The machine will then leave the browser and go to desktop or shutdown or lockup. Need help with what the files are missing or needing to resolve this issue.