Preaching to the Spirits in Prison

Many theories have been advanced concerning what is meant 'by whom also he went and preached to the spirits in prison.'

Unbiblical theories have abounded, especially in our day -- the most common among evangelicals being that Christ went into some sort of secondary compartment of 'Hell' that bordered the place of suffering.

We believe that interpretation is absolutely incorrect and does damage to the doctrine of eternal punishment.
WHO went and preached?
WHERE did he preach?
TO WHOM did he preach?
WHAT is the identity of the 'ones who were formerly disobedient' but are now 'in prison'?
WHEN did this preaching take place?