Playback bug. Sound is crackly, quiet, and laggy.

This happens to anything I write. When I play it back, it is laggy, the sound is crackly, and it is much quieter than if I click on a note to make a sound. The thing it seems like at a first glance is that my computer is not strong enough, which is why it would be laggy and the sound crackly. Stuff like this happened on my old computer, but I've never had this happen on my new one which is soooo much nicer and can run video games that are way more tasking with no problems. I just can't use the program.