I presume you are using LW 5 right?
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Right-click the column heading bar in library & you will see options to show more columns. Then click or doubl-click the particular heading you wish to organise your files by;
Arranging LimeWire 5's Library to see More Options; Uploads, Bitrate, etc.. That way you can organise music via artist, album, filename, etc.
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eg: click the Artist heading to arrange them that way alphabetically.