There are two ways to speed up a video clip in Sony Vegas. The first way is to right click on the clip itself and go to properties then playback rate and up that number. I believe it maxes out at 4x.
The second way to speed up a video clip in Sony Vegas is to select the clip itself in the video timeline then hold the CTRL key and drag the clip toward the left. I prefer the second method because I can visually see that the clip has changed in the timeline. In the first method you will not see a smaller clip but you will see swervy lines to indicate a change.