longear: thanks for the advice, jpgalleg 2.5 grabber plugin does work with allegro-4.0.3
I built allegro 4.0.3, I then built jpgalleg 2.5, then I built the grabber plugin, and made a copy of the grabber.exe and dat.exe. I then removed allegro 4.0.3, stuck on allegro 4.2.1 and built that, then built jpgalleg 2.5 against it.
I then built a simple test program that checked if data files created with the 4.0.3 grabber could be used by the 4.2.1 dll. The test worked fine, I hope that it doesn't have any problems.
This zip contains the grabber.exe, dat.exe, allegro-4.0.3 dll, a compiled jpgalleg 2.5 (against allegro 4.2.1), allegro 4.2.1 dll and an example program.
the example needs to be linked against '-lalleg' and '-ljpgal'
In jpgalleg, you need to copy the include directory to the mingw include directory and the lib\mingw32 to the mingw lib directory.
If you arnt using 4.2.1, you probably will need to recompile jpgalleg against whatever version you are using.