How can I change the details in my music folders such as genre, album, artist, etc?

You can not do this to the folders. This information comes from the files id3 tags.

You wold have to edit the files id3 information so that it displayed correctly in the folders.

If this is windows and you have windows media player 11, you can go to your library and highlight all the files at once. Then right click and select advanced tag editor and fill in the missing information. Make sure you don't highligt a group with diffrent attributes, like diffrent artist or album.

If you are making your own mp3's from cd's make sure it can retrieve the album information online. Then this information will be added automatically when creating new mp3's.

Here is a shell extension that will add id3 tag editing to Windows Explorer:

As this info is in each individual file, there is no magic bullet to make them all correct in one wave of a wand. I had once tried a unility that claimed to be able to update the id3 tags automaticaly, from it's database. But it failed a majority of the time and often gave the wrong information. That was a ugly mess.