[InstallSettings]
InstallPath MinGW=G:\MinGW
InstallPath=G:\MinGW
That's my mingw.ini file. What happened was I first installed the candidate version, 3.2 I think, and it wrote the first line. It did not work. It said it was expecting an '='. So then I downloaded the current, 3.1? version, installed it over it, and it seems to have added the second line.
I just tried deleting the first line, but the detect feature still doesn't catch it.
What I did was I entered the path manually, and replaced all programs with their full paths, and everything works.
Maybe it would be easier for you to scan the file backwards, one past the first occurrence of ':\' (colon-backslash)