It shows for me as well in the status bar on WinXP SP3. I remember a time when it didn't though I had to jump through some hoops to get it to display again, but I can't find any info on how I did it anymore.
I wonder if it's not a setting within some media player or media info app, like Winamp, WMP, or Media Info, GSpot, etc.
Edit: Found one program for me that makes a difference with a setting.
MediaInfo has a setting in Options/Preferences, Setup, for "Shell InfoTip". Without that option checked, I get very limited info, only the codec and file size. With it checked I get the full info including time of the mp3 file (or any media file).