Q: The music folder on my hard drive shows a sub-folder for each album. When I added the entire folder to iTunes, they’re listed in the library under one unknown album and not grouped together by artist at all. How do you group the songs back together as albums?
A: The most likely cause of this problem is that your songs do not contain any actual album or artist information within the tracks themselves.
When iTunes imports music, it does not at all care about the name of the folder that it is coming from. Instead, it looks inside the MP3 file headers for something called an “ID3 Tag” which stores information such as artist, album, track name, and so forth. If an MP3 file doesn’t contain any information in a certain field, then iTunes has no way of knowing which album its from and just considers it unknown.
The best way to solve this in your case would be to get the tags filled in before you import your music into iTunes. There are applications which can fill in these tags based on your file and folder names for you automatically as a batch job. Check out either MP3tag or Tag&Rename for a couple of good options to help you with this.
Once the tags are properly sorted out, you can then import your music into iTunes and it should be able to organize the artist and album information properly for you. If any information is still missing at that point, you can fill in the tags via iTunes and it will also write this information back into the files themselves for future reference.