Does iTunes modify mp3 files?

[f0rbez]

The main problem I have with Windows Media Player is that it modifies the ID3 tags of any mp3 that you open. Even if you go into the options and deselect any options related to the updating of ID3 tags, it still does. So I've stayed with Winamp because I know that it is "safe". It won't update my files unexpectedly. Now I've downloaded iTunes but I want to be absolutely sure it does not modify files before I load my mp3 collection. I chose not to update files when installing but I just need to be positively sure that it won't update anything at all. Have any iTunes users noticed it changing files when its not supposed to?