Predictive mode requires compilation:
To install the package, extract the files using tar -xvzf predictive.tar.gz. This will unpack the files in a new directory called predictive/. Now byte-compile all the Lisp files and create the required dictionaries by running make in the predictive/ directory. If necessary, you can specify explicitly where your Emacs resides with make EMACS=/path/to/emacs.
-- Installation guide from the official website
This installation requires make utility. You can obtain it with Cygwin, which works well and compiles all dictionaries, including LaTeX dictionary. At the same time, make from GnuWin32 gives out some errors and fails (probably some dependencies are lost). So, Cygwin is the one.
After you've installed Cygwin, run Cygwin Bash Shell and go from there to your
~/emacs.d/predictive directory. Cygwin link local drives to
cygdrive directory, so in your case, the path will be
/cygdrive/c/program files (x86)/emacs/.emacs.d/predictive/latex.
After you've reached the
make and Enter. If Emacs's bin directory is in Windows' PATH environment,
make will find it and will compile dictionaries. Otherwise, like the official guide says, run
make EMACS="/cygdrive/c/program files (x86)/emacs/bin/"
Make sure .emacs file has both lines:
(add-to-list 'load-path "~/.emacs.d/predictive/")
(add-to-list 'load-path "~/.emacs.d/predictive/latex/")
At this point LaTeX dictionary should work and the English dictionary be much faster (without compilation they're a little bit jerky).