Your safest option in general is to use the slapcat utility. This will produce a portable file containing all the information you need to reconstitute your server.
The concept is:
- run slapcat to take the backup (i.e. slapcat -n 1 -l backuplocation\backupfile.ldif)
- transport the backupfile.ldif to a backup location
- done
This can be done with a scheduled task easily enough
The important details of actually taking the backups depend on how you installed OpenLDAP on the windows system. A quick search indicates a number of windows ports of OpenLDAP.
How is LDAP setup?
What database are you using? bdb and hdb are safe to slapcat against while running
Sorry, but your question is pretty open ended.