I'm looking for the best software to manage files (documents) by using their metadata, somewhat like music libraries manage mp3-files.

I would like to manage the whole of my office documents the same way (author, user, branch, sercice, created, modified, todo date, keyword, etc...).
It should be possible to use such soft for the management of the complete filetree on a PC.

I'm sure there are some goeroes out there, who know a lot about it. Care to share some experience? If this is not the right forum, do throw we out.