Original files not tagged

Okay, I'm totally new to this. I have a file I downloaded that was missing many of the tags, so those tracks wouldn't import into iTunes. Then I discovered mp3Tag, imported the songs, retagged, and all seemed great! But when I went back to the original files, they hadn't updated. I tried the export command, which didn't address my issue. I'm sure I'm missing something simple, but I couldn't find it in the Help section of the program, nor here (and I did try Searching before I asked).

What am I missing?

Thank you!

Sled

How do you go back to the original files? Didn't you tag these files?
WHich program does not show the entered tags? Itunes or MP3tag?
What do you mean by tagging? Renaming the file?
Where did you modify the tags? Only in the tag panel? Have you pressed Save after entring the modifications? (export is not the function you are looking for - you are operating on your live files, so any information is updated immediately if you press save or lost for ever. There is no database that stores the information first).

Anyway: I think your description of your proceedings do not tell the whole truth.

My original files are in my music folder. They show the song name, some show the band name, track #, etc, and some do not. That is why I am using mp3tag. When I added all the information for all the tracks in mp3tag, I clicked save, and it still shows all the tags, but only in mp3tag. My original music files in my on my music folder has the same incomplete information as when I started.

with which tool do you look at the saved information?

The next step will be the following anyway:
Take one of the unwilling files and load it into mp3tag.
Then select the file and press Alt-T to open the extended tags dialog.
Check if the dialog title says something like ... APE ... (not not only MP3 Vxxx).
If you find APE then your source has written APE tags and they overrule MP3 tags.
have a look at the follwoing thread dealing with APE tags
[X] Mp3tag Does Not Read These Tags...

Thank you, I will try that tonite. As far as the files go, all I'm doing is opening the file from my desktop to view the track names, not using any tools.
Thank you very much for your help!!

Now I think I get it:
Do you expect the filenames to change? Well, they don't automatically.
THen you would have to use the function "Tag - filename" and enter a mask consisting e.g. of
%artist% _ %album% _ %track% _ %title%
Try this.