This isnt a tweak, but a great little feature that comes with Windows XP that you might not realised yet. Here’s how to convert your digital photos into a your own personal screensaver. I recommend you to add text to the photo first to give more personal look such as where and when is the picture had been taken.
1. Right-click an empty spot on your desktop and then click Properties.
2. Click the Screen Saver tab.
3. In the Screen saver list, click My Pictures Slideshow.
4. Click Settings to make any adjustments, such as how often the pictures should change, what size they should be, and whether you want to use transition effects between pictures, and then click OK.
Now your screen saver is a random display of the pictures taken from your My Pictures folder.
Alternative: You can use this tool which has a feature to add MP3 into your personal screensaver but adding audio files to screensaver is not recommended for slow computer.
http://www.programurl.com/happy-note-my-mp3-screensaver.htm