You can choose columns in Windows Media Player; right click in the header field, then click "choose columns". You can resize the columns, drop unwanted ones (5 stars etc) rearrange column order, and add one or two custom columns if you wish.

The main drawback to adding custom columns I have found is that you end with an over-detailed display if the comments are of more than a word or two. If you want to make extensive notes I suppose that a reference number in the custom column referring to a separate comments database might be one way to tackle it.