What follows is a very brief overview of the Registry and its functions.
More details can be found (at the time of writing, February 2006) at:
An internet search will also reveal many other useful resources.
In the 'good old days', hardware and software installed on a machine would mostly have its own Initialisation Files (eg config.ini), text-format files containing various information relating to its owner, configuration etc. Unfortunately, these became scattered across the directory structure, each with its own schema. There were also limits on the size of these files.
These factors, together with a massive increase in the amount of information needing to be stored and accessed quickly led to the development of the registry as a centralised, standardised repostitory of information related to the computer's hardware and software.