I got this problem as described by the link below,
and I was suggested to try opening the file using command prompt.
Here was what i did,
Is that how we run an exe. using command prompt? Or I have misunderstood something?
Your problem is command prompt does not know anything about spaces in file names.
it thinks your exe name is FLTK and testing as a paramter to your application.
if you try "FLTK Testing.exe" with quotes as written it will probably run.
but i suggest that renaming your exe without spaces for easy access.
also if you press F and Tab probably command prompt encapsulates file name in quotes (") automatically.