To be able to add the Active Directory Schema Snap-In at an MMC you need to register thschema management dll. To do so, open an elevated command prompt and run:
Pantelis Apostolidis is a Solutions Architect professional at Office Line SA and a recognized Microsoft Azure MVP. For the last 10 years, Pantelis has been involved to major cloud projects in Greece and abroad, helping companies to adopt and deploy cloud technologies, driving business value. He is entitled to a lot of Microsoft Expert Certifications, demonstrating his proven experience in delivering high quality solutions. He is an author, blogger and he is acting as a spokesperson for conferences, workshops and webinars. He is also an active member of several communities as a moderator in azureheads.gr and autoexec.gr. Follow him on Twitter @papostolidis.