Don't think it would be smart to delete. Read on...
Hives are the major subdivisions of all of these subtrees, keys, subkeys, and values that make up the Registry. They contain "related" data. Look, I know what you might be thinking, but this is just how Microsoft divided things up -- I'm just relaying the info, even I don't know exactly what all the advantages to this setup are. ;-)
All hives are stored in %systemroot%\SYSTEM32\CONFIG. The major hives and their files are as follows:
You could say I've been around.