Probably most of You know it but I came across it just today – in case that You will look for test environment for OpenLDAP and there is no Linux box nearby or You don't want to play with source code You can just download ready build of OpenLDAP for Windows. This build was prepared by company called Ilex.
I had to build test environment for MIIS OpenLDAP MA and I came across this build. I've tested and it works OK. In case that You will need quickly test something with OpenLDAP this is easy way to do this.
Little update – I was contacted by representative of Symas and I get to know that there is also OpenLDAP build for Windows available from them after registration. Connexitor™ Directory Services is compatibile with OpenLDAP 2.3.3x, so if somebody is in need of such build go and get one :).