Rebuild entire database?

[Kupuna]

I've used MM for several years and lately my database is showing a large number of "ghosted" greyed-out tracks that are no longer available. The database is also referencing tracks from an older hard drive that failed. I can understand that data being retained, but I can't seem to get rid of the ghost tracks.
I think I need to remove the old DB and start over. Is that a wise decision?
I have pockets of music in various locations on my PC and external hard drives. Should I consolidate those before rebuilding. Also, I have an iTunes database that seems to put everything in layers of parent/child folders. Will MM search to that depth of folders when automatically scanning for a new installation?
Just recently I've been getting a "thread creation error...not enough storage is available to process this command. Is this another reason to start over?

[Lowlander]

Remove greyed files from the Files to Edit > Dead Links sub-node and unavailable drives from the Location sub-node.

You can use File > Clear Database, but you'll loose unsaved tags, Play History and Playlists as well.