If your download file is only "We Will Rock You" and "Summer of '69," you have a party playlist, not the 500 greatest.
Always keep a copy on an external drive or cloud storage.
: Nirvana, Pearl Jam, Radiohead, Green Day, Rage Against the Machine.
If you are looking to assemble your own archive of the 500 greatest tracks, curation is key. Rather than downloading blindly, consider organizing your library by sub-genres to match your mood: