first select the first slide, then execute "insert → movie and sound → sound in file" to select the file you want to insert, and select "automatic" in the pop-up "how do you want to start playing sound during slide show". At this time, a trumpet icon will appear on the slide. Right-click this trumpet to select Custom Animation, click the drop-down button in the task pane on the right, select Effect Options, select "Stop playing after 99 slides" in the dialog box, and then set "Repeat" to a larger value in the Timing tab, so that your slide will have background music.

PS: If the small speaker icon affects the display effect during the slide show, you can drag and drop it out of the slide show range. When you need to play this slide on another computer, you'd better package PowerPoint, or copy the sound files to the new computer and set the appropriate path

If it's not your problem, it's your classmate's computer. This is difficult for me to answer. There are many questions that can't be played.

1. you need a player to play music. Powerpoint itself does not have a player, but uses various player plug-ins. If a player plug-in is not installed, it cannot be played.

2. There are two ways to insert sound, one is embedding and the other is linking. If it is linked, you must copy it together with the music files.

3. Embedding or linking is actually optional.

tools-options-general, there is a "link sound file not less than" in the general option, and the default value is 1 (in k), which means that if the sound file is less than 1KB, PowerPoint will automatically embed it in the PPT document, and if it is more than 1, just make a link.

as long as this number is larger, that is, larger than the sound file, the sound file will be automatically embedded in the PPT document. However, this will cause the PPT document to be too large.