Neowin reports Microsoft now allows PEGI 18 games in the Windows Store, meaning European gamers can now download mature content via the Store for the first time. So far only two games are available though; Grand Theft Auto IV and The Witcher 2.
Two major games are now available for Europeans via the Windows Store: Take Two's Grand Theft Auto IV, and CD Projekt RED's The Witcher 2. These games were previously available only for those people outside Europe, as both games are rated PEGI 18 and weren't allowed in the Store until now. If you're a parent and you're worried your child might access these games, there are parental controls built in that can filter out mature content from the Store.
Of course it should also be noted that games such as Grand Theft Auto IV and The Witcher 2 have been available in Europe through other game distribution platforms, such as Steam, for some time now.