Please Help -> Sound level equalization - Destroyed Tracks!!!

[SVB]

I recently installed iTunes on my Pc and after spending a while adding approx 20Gb worth of music to the Library from the hard -drive (I am sure this could be made easier but that is another issue!) I selected the 'Equalize volume' option and allowed the ipod to sync.

Now, when I listed to tracks the base and trebble is ok but the mid-range, ie any vocals, is really faint and can hardly be heard.

1) Has anyone lese had this experiance

2) How can I reverse the equalisation without deleting all the tracks from the library, syncing an empty library and then stating again.

Any help / suggestions much appreciated.