Hang on, the .itl file does not contain your music. Instead, its a management file that iTunes uses to keep note of where the music files are located. You need both the .itl file, and the actual music files and there is no way that 574KB is all your files.
I'm not the expert on this, but as an example, my iTunes Library needs the following files (all of which should be used for your new library). Note that the "date" in the file name will be unique to your library, so unlikely to be the same as mine which is 2011-11-16:
- the iTunes Library 2011-11-16 (the .itl file). My current one (updated today) is 25,753KB
- the iTunes Library 2011-11-16 Extras (a .itdb file). Mine is 440KB
- perhaps even the iTunes Library 2011-11-16 Genius (also a .itdb file - even though I don't use Genius). Mine is 32KB
- all the music files, which will probably one of the following file extensions:
- MP3
- m4a (this is Apple's own format, sometimes known as AAC)
- FLAC
- WAV
There are other file formats, but those are the most likely.
I have a large library, which may explain the size of the .itl file for it (at 25,573KB). While 574KB might be correct for your library, it is not the music. A typical song, three minutes long, in MP3 format, would be anywhere from 2.2MB (that's 2200KB) to 8.1MB (which is 8100KB). Don't forget, many of your songs are likely to be longer than three minutes, which means a larger files size for those files.
Hopefully, all your music is in the Music/iTunes folder, along with the .itl file. In my Music folder are various sub-folders which have the music and the .itl files. So my backup (and what I will use when I create a new library) is the Music folder.