Hacking Windows XP: Speed Up Your Boot

Hacking Windows XP: Speed Up Your Boot: "Windows XP includes a boot defragmenter but it is a little tricky to get it to run. By default, it is run only in the background and cannot be started directly by a user. After your computer has been idle for some time between 5 and 30 minutes, the system will read the prefetcher's boot data and start the defrag. The system defrag is run in the background and is invisible to the user. Eventually, if you leave your computer on long enough, it will be defragment the boot files
Microsoft has a very talented team working for them and they even took into consideration that often your system boot changes. For example, you might install an updated device driver or add new hardware. To solve this problem, the system will re-defragment the boot files every three days.
Tip:
Windows keeps track of the last time it optimized the boot file so that it can calculate how often it should run the boot defrag. If you are interesting in finding when the last time was that the boot defrag was run, open up regedit and navigate to: 'HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Prefetcher' and then look for the key named 'LastDiskLayoutTimeString'. "