On my Windows 8 system, I renamed the DLL. Unexpectedly emacs
launched, and it exited normally. According to Process Monitor, emacs failed to find this DLL anywhere else. I doubt that I have another copy but I am searching the C: drive now.
I have *one* copy (not in my path) in a directory in which I had assembled all the files required by a small program that I wrote, including this DLL and
libstdc++. On XP, even though the DLL is in the PATH, it is not loaded when
emacs runs, according to Process Monitor.
The XP system contains only the files in emacs-24.4*.zip. I have added files
(usually extra modes) to my main emacs installation over the years, although
I would not be able to say what I have added. If there is another startup file that is read besides .emacs, that may be answer.