Taking Care of the Widows and Orphans

The Torah tells us no less than twelve times not to oppress the widow and the orphan. The Sefer HaChinuch connects it to the previous mitzvah, not to oppress the convert and gives a similar reason. It’s severity is indicated by the fact that it is one of the few mitzvot where the punishment is included with the mitzvah.

To what extent is one expected to give preferential treatment to a widow or orphan? When does a halacha change because the subject is a widow or orphan. How does this mitzvah differ from the prohibition against oppressing others?