ExtremeTech offers some help on speeding up the startup time of Windows Vista:
Because Windows Vista optimizes itself to store the most-executed code on the fastest and most accessible portion of the hard drive, the load time can theoretically decrease with regular usage. Unfortunately, that notion is defeated by actual, realistic usage. As you install programs, many of them come with their own services or start their own processes on bootup. Before long, Windows Vista demands a solid two minutes of your time from the moment you push the power button until the OS becomes useable. So let's do something to speed up this process, shall we?