The \Data\settings folder does not exist until GimpPortable is run without the .ini file. This first run will create the settings folder if it is not there if you run it without the .ini file.
The error is as follows:
GIMP Portable | PortableApps.com
D:\%pathtoGIMPPortablefolder%\Data\settings was not found. Pleas check your configuration
You can also create a settings folder manually to resolve this if you're using the ini file.
Simple answer: You must run it once before using an INI. About 1/2 the apps work like this.
Sometimes, the impossible can become possible, if you're awesome!
I was going to say that, but couldn't remember if it was just mine, or yours too
Anyway, if it did work with custom directories, you'd have to specify a DefaultDataDirectory option in the INI and it would add a lot more code.
----
Ryan McCue.
Blog.
So all that Airbus-delay trouble over here in Europe is because of YOU!
Simeon.
"If you're not part of the solution, you're part of the precipitate."