Question: I need to setup a LDAP-Server on my windows (7) machine for development purposes.
How do I do that? And how do I get data in there?
There is apparently an OpenLDAP bundle for Windows.
You could also try ApacheDS.
Regarding data access, Apache Directory Studio (standalone or as an Eclipse plugin) is fairly good (it's not specific to ApacheDS, it works fine against Active Directory and OpenLDAP serers too, for example)
There's also AD LDS (Lightweight Directory Services) - used to be ADAM (Application Mode)