The topic was supposed to say:
"iTunes not recognizing MP3 files" not shopping!

I put in 5000 songs into Itunes.
2400 show up.

Do you need to mass convert all tags from ID1 to ID3?
I have never been able to use these mac systems.

All playing in the PC with Winamp and Zune software.
THEY are all mp3 by the way.

Isn't this an off-topic as it concerns iTunes?

No, you don't have to convert the tags as iTunes usually does not have problems to read these tag types.
How do the files look like in MP3tag? Do they show the information there?
In what way do the bad files differ from the good ones?
Are they stored on a different device?
Have you (accidentally) applied a filter in iTunes (top right of the window)?
Does a check with foobar2000 or mp3val show any maladies?

There are so many possibilities ... you have to help a little.

Thanks for the help,

mp3val does show tons of errors, mostly bad MPg frames or gargage at end of file.

I was afraid to use the correct feature on mp3val.
mp3val is totally safe?

MP3tag shows all files normal, nothing I can tell thats wrong.

Oh, well ... it has helped me lots of times - just like foobar has.
Yet, it very much depends on the kind of corruption.

So, what I would do:
Repair only one file with mp3val.
Reload it into MP3tag and see what is left of the tags.
then import it into iTunes and see what iTunes makes of it.

Continue if this way leads to success.