By default, PowerPoint will output a jpeg at 96dpi (click the File menu, Save As, and choose jpeg as the type). This is fine for the Web, but not for printing. In most cases, you’ll need at least 300dpi.
To create high resolution jpgs, you have two choices…fiddle with the registry and change it, or invest in some very inexpensive software that will do this for you. To complete a recent project, I chose the latter (I highly suggest you do the same).
The ImageExport on the PPTools Website is a fast, easy way to export graphics from PowerPoint as a GIF, JPG, PNG, or WMF at various resolutions. It’s $29.95, and you can try it for free.
For more tips in PowerPoint, buy my book, Just Show Me Which Button to Click! in PowerPoint 2007 and another one on PowerPoint 2003 or enroll in one of my PowerPoint workshops.