I'm sure with Imager, you are supposed to specify the libraries and the search paths when running the Makefile.PL. If that doesn't work, you will have to show the console output of what happens when you run Makefile.PL.

Yes, I've tried to specify where the libraries are (via command line and by hardcoding them in the makefile) - in fact, I used the README's exact example and got an error:

'IM_INCPATH' is not a known MakeMaker parameter name.

Here's an example of the console output:

Set up gcc environment - 3.4.5 (mingw-vista special r3)

done.
       gif: includes not found - libraries not found
     ungif: includes not found - libraries not found
      jpeg: includes not found - libraries not found
       png: includes not found - libraries not found
      tiff: includes not found - libraries not found
 freetype2: includes not found - libraries not found
 freetype2: not available
  T1-fonts: includes not found - libraries not found
  TT-fonts: includes not found - libraries not found
       w32: includes not found - libraries not found
EXIF support enabled
'IM_INCPATH' is not a known MakeMaker parameter name.
'IM_LIBPATH' is not a known MakeMaker parameter name.
Writing Makefile for Imager::CountColor
Writing Makefile for Imager::Filter::DynTest
Writing Makefile for Imager::Filter::Flines
Writing Makefile for Imager::File::ICO
Writing Makefile for Imager::Filter::Mandelbrot
Writing Makefile for Imager::File::SGI
Writing Makefile for Imager::plugins
Writing Makefile for Imager
[download]

I guess basically what I'm looking for are step by step working instructions to install JPEG support in Imager. Unfortunately, everything I find online either doesn't work or is written for *nix.