Well, since you're a *nix guy, you could always just pop in one of those Linux-on-a-bootable disks and use this command (change the last part to where you want to move them):

mv -r *.mp3 ~folder/mp3

And that'll find/move all mp3 files recursively.

Or in windows, use the Xcopy DOS command. Here's a full reference: Clicky

It'd end up looking something along the lines of:

xcopy C:\*.mp3 new_folder /e/i/h/y/d/exclude:files_to_exclude

Or maybe the Windows search just isn't beefy enough to handle the task, so there are tons of freeware search/find Windows utilities that you could try. Just search for *.mp3 recursively, in the results window press CTL+A to select them all, and drag and drop them (or use the Move command if the program offers one, or cut/copy/paste, whichever is your preference) to the final folder. Here's a possible one, although I've never tried this program specifically myself: Clicky

Here's a site with a list of a bunch of search/find Windows utilities in case you need to try others. Clicky