Is there any tool that can scan MP3 files and tell the bad ones apart from the good ones? I am particularly interested in picking out the ones with bad headers and ID3 tags. If there is a tool like this, can you tell me where I can downlod it? Thanks everyone.

One tool is EncSpot. Not supported anymore, but still available and works reasonably well:

EncSpot @ CDRW.org

I use WMP9. The bad ones are the ones it won't play.

Have you tried playing "bad" MP3s that WMP9 wouldn't play using another player like Winamp/Foobar etc?

I would be curious to see what you find because WMP9 (in my experience) is not a very good MP3 player, espcially with VBR MP3s. It can't FF or RW, shows bitrate incorrectly which makes me suspicious of how robust it is for playing problematic MP3 files.

You can try the brute-force method with VBRfix with the option "Fix a dir of MP3s". It will repair all files with a corrupt VBR header and optionally deletes ID3v1/v2 tags, too.