Windows XP contains several things to help boot time.

This page goes into details on what is done:

Boot Prefetching
Windows XP speeds up system boot by observing the code and data needed each time the system is booted and prefetching the necessary file contents early in the boot process. This prefetching is not done until the third boot of the system, when sufficient information is available to make the prefetching most effective. The files observed during system boot will be used in the disk layout process mentioned above. Additional information on the prefetcher and the Windows XP boot process can be found at Fast Boot/Fast Resume for the Windows Platform.

BootVis forces most of the optimizations explained on the website above to run manually. If you read the above page you will plainly see this is definately NOT the most optimal thing to do.

The best thing to do is install your apps and just start using the system. Once it gets enough info about usage patterns it will start optimizing itself. (ever notice your hardrisk start running when your not doing anything? Its not always the Indexing service........)

The boot optimization routines invoked by Bootvis.exe are built into Windows XP. These routines run automatically at pre-determined times as part of the normal operation of the operating system.