If you use elastic audio, you can slow it down without affecting the pitch, though the sound will not be perfect.
To do this, (assuming you're working with one stereo track) put the track into Polyphonic elastic audio mode. This is found in the edit window, underneath the name for the track.
Now change the track to be a tick based track - again it is under the name of the track in the edit window.
Now simply change the tempo of the project, and the track will match.
If you're trying to get rhythm and timing correct, and are not bothered about pitch, Benny's method is the best.
Finally, the other method I can think of is to press control and then a number on the keypad - 5 being normal speed, and 4 being slower, 6 being faster. This is from memory mind... Again this will affect the pitch.