You might try this:
(The Godfather - Freeware)
(You might need to use something other than IE to go to this page)
It is one of the most powerful taggers I have found. You can recurse subdirctories, so all you have to do is go to the top level, tell it which file tokens to use for each field, and update. I have tagged about 1500 files in less than 15 minutes.
It does take a bit of getting used to. Just remember to re-scan the directory before each change if you aren't seeing what you expect. And there is a bit of a learning curve, but I found it well worth the effort.