I can't find the mfcinst71.exe dll
Well, mfcinst71.exe is an executable, not a DLL for starters. Not that I'm poking fun at you at all, more at the idiots who phrased things in such a confusing way. I
suspect what they are talking about is an installer for something called MFC 7.1 (MFC = Microsoft Foundation Classes). Unfortunately, even this doesn't seem to exist as something separate (and Microsoft are a complete pack of idiots for not making this easier for end users coping with products from software developers who have dropped the ball). It seems what you really need to do is search for
mfc71.dll download.
Why you have to download Microsoft runtimes from sites other than Microsoft I'll never understand. (Try that exact same search string in the search bar at
Microsoft's home page and see how far you get.) Surely for anyone making products with so many security holes the last thing they need is their runtime DLLs being supplied by sites of unknown provenance. Who knows what may be patched in?