I hope this is responsible for the frequent crashes I get with Emacs 25,
or at least most of them.

I spent many hours narrowing this down.  I'm hoping that that time won't
have been wasted. ;-)

Recipe:

1. Save the attached file, `e25-crash.el'.

2. runemacs.exe -Q --debug-init -l "/YOUR/PATH/TO/e25-crash.el

You will get two frames, one with buffer *scratch*, the other with the
minibuffer, buffer *Minibuf-0*.

3. Click the title bar of the frame having buffer *scratch*, to raise
and select it.

4. `C-h f prefix-command-preserve-state RET'.

5. Click `mouse-2' on the file name `simple.el' in buffer `*Help*'.

CRASH!

Note that using a different command for `C-h f', which is not in
`simple.el', might not crash Emacs.  A guess is that the (now)
large size of `simple.el' contributes to the problem.

In GNU Emacs 25.1.1 (x86_64-w64-mingw32)
 of 2016-09-17
Windowing system distributor `Microsoft Corp.', version 6.1.7601
Configured using:
 `configure --without-dbus --without-compress-install CFLAGS=-static'