You can do the reversing in Vegas. You can't create the starfield itself though. Vegas is an editor, not an animator. Perhaps a screen recorder could be used to record Window's screen saver and produce an .avi file. Place this .avi file on the timeline, right-mouse-button click on it, and choose Reverse.
If you want to delve into creating starfields and much, much more in ways you can customize, color, direction, etc,go look at Particleillusion. A very versatile particle emitter program that comes in SE and Pro versions.