Take a look at MusicBee.
Simply select all the files in the library->Right click menu->Auto-tag by track->Identify track and update tags.
Now you can choose to update files based on digital sound signature or not, update blank field only or all etc
Also, from http://www.techsupportalert.com/best-free-mp3-tag-editor.htm :
Mp3tagMp3tag is a good choice if you prefer to have a user interface
with a normal windows menu. Mp3tag has the advantage of a simple and
clean design with a powerful and yet easy-to-use tool to edit tags of
Basic tags are shown in a customizable front panel. Extended tags are
shown in a separate window for all existing tags stored in your MP3
files. If a tag for lyrics or other info does not exist, it can be
added, or if a tag is repeated, it can be removed easily.
Mp3tag allows you to rename files based on the tag information, import
or export tag information and create playlists.
It supports online
Amazon, freedb, MusicBrainz and other database look-ups, allowing you
to auto tag and embed multiple images for album covers.
It also has a powerful Web Sources Framework, allowing you to get
album info from additional online databases. The latest web sources
are available from Mp3tag Forums at Web Sources Archive. You can
download the ones you need, and extract them to your Mp3tag data
folder in order to gain access to more online databases for auto
I used this one a year or two ago, to do what you are trying to do and it worked.
MusicBrainz PicardMusicBrainz Picard runs on multi platforms and
adopts a new tagging concept that is album oriented, as opposed to
tracks or files oriented tagging.
It identifies track information by comparing a unique digital
thumbprint to the information in the MusicBrainz database. Once the
tracks are best matched, you can save their respective tag information
into selected MP3 files. How To Tag Files With Picard is a helpful
guide for a quick start.
As with Mp3tag, checking the details of a selected file evokes a list
of all existing tags, including lyrics, which you can then edit. If a
tag doesn't currently exist, you can always add it.
But in the version under review, cover art edits aren't possible
except by updating from online databases.