Boot files are not "usually" defrag-able. Some are in the Master Boot
Record (MBR) and the others are usually at the beginning of the boot
disk Windows partition. Not only this, but if the PC were to
"hang"/"reboot" during the defrag of these files, kiss your Windows
"goodbye" as it will not boot after.
Also, the built-in MS Defrag system does not seem to touch the "page
file" so it would not touch the boot files.