I am corresponding with a relative whose great grandmother was Abigael de Vries b. 1832 who married Coenraad Eliezer Gomperts. In a message from Iwan de Vries mention is made of "a small group that digitalizes all the data they can lay hands on, so I have a lot of databases right on my HDD." How do I communicate with Iwan de Vries in an effort to obtain additional information about Abigael de Vries? Please tell me what "HDD' means. Thank you for your response.