[quote="plexicrunch"]Thanks. So it looks like for FLAC files, the tags should be stored with the file and MM should be fine, but there's no guarantee that any other application can use them, correct?[/quote]
Read the table:
http://www.mediamonkey.com/wiki/index.php/WebHelp:About_Track_Properties/4.0

Anything with "Yes" should be able to be read with other applications because it is the standard for that format. If it says "Non-standard" then there's a chance other applications will not read that particular tag, because it is not standardized for the format.

Most tags MediaMonkey saves are according to the common standard for the file type. Thus generally other applications should be able to read the tags.

Thanks. So it looks like for FLAC files, the tags should be stored with the file and MM should be fine, but there's no guarantee that any other application can use them, correct?

It depends on the file format if custom tags are saved to the files themselves: http://www.mediamonkey.com/wiki/index.php/WebHelp:About_Track_Properties/4.0

It may be beneficial for you to give this wiki page a read: [url=http://www.mediamonkey.com/wiki/index.php/Moving_MM_to_a_new_computer]Moving MM to a new computer[/url]

make sure to have no unsynchronized tags before moving the files: http://www.mediamonkey.com/wiki/index.php/WebHelp:Synchronizing_Your_Tags/4.0

It looks like I need start on a fresh machine and am hoping that the act of moving my music files to a new HD and MM library won't result in the loss of the custom tags I've used. Can anyone tell me if this will work? Thanks!