Captain Chaos:
For checking the structure of the MP3 file itself, including VBR headers, you want
MP3TRIM. This will tell you if the file is a "good" file or not. If MP3Trim gives the file a clean bill of health, then it should play on any playback software. Note that the free download version only works on one file at a time, and it has a file-size limit. The pay version does not have this limitation.
For playing with ID3 tags and straightening them out, you want
MP3 TAG STUDIO. This is an incredibly powerful tool that allows you to do rule-based processing on every tag in your MP3 folder.
For looking at the bit rate and quality of all your MP3s as a group, you want
ENCSPOT. This will tell you what encoder was used to create a given file and will make a judgement call as to whether it's good quality or not.
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Tony Fabris