Asterisk-win32 is 1.2 based, so you need to build the old version from
http://www.readytechnology.co.uk/open/ipp-codecs/
Here are the files
http://asterisk.hosting.lv/mirror/ipp-svn6.diff
http://asterisk.hosting.lv/mirror/l_ipp-sample-speech-coding_p_4.1.008.tgz
To build against IPP 5.x you need to tweak the source a little bit:
ippCoreSomething() -> ippSomething(), IIRC.
Asterisk-win32 port is using Cygwin, so the codec compilation should be quite
painless.
If you wish, I can send you an archive of the tree I used to compile the codecs
for 1.2.
Please contribute the binaries when ready.