Here's an informative post:

http://daredreamermag.com/2011/02/23/how-to-legally-use-music-in-your-films-and-videos/

I suppose a strict reading of the copyright would restrict the music to your own personal use in your own equipment.

If you put music on a video or slideshow that you don't post on-line... no violation at all.
If you put music on a video that's just for fun and you're not a professional and you don't get any money at all and it doesn't go viral - tiny violation that nobody cares about.
I always put a music credit at the end of my videos. I use Vimeo though and hardly ever post to YouTube.