The MCD is the wrapper of all MS Office traditional documents, such as .doc, .xls, .ppt, and .vsd. A MCD container can be imagined as an array of slots, where each file stream is chopped into sections small enough to fit into the slots, and the slots comprising a file are linked into a list. In other words, the storage is managed in a way similar to how files are stored on hard drives. Just like a file allocation table on a hard drive, there is a similar allocation table that manages the sections. Likewise, a file index table is used to retrieve the files inside the container. This concept is quite old, though. It represents the typical thought of software engineers of 1980s when they must deal a lot with hardwares and algorithms.

A thumbs.db file contains a catalog, which provides information of which names are mapped to which files – and these files are thumbnail images in JPG formats. With Virgo Viewer you are able to extract all thumbnails from that .db file.