Just read the readme file for an update of PerfectDisk:
What's new in PerfectDisk build 7.00.042
* Clarified some of the boot-time defragmentation messages.
* Changed PerfectDisk's boot time defragmentation code to be consistent with changes made to check disk (chkdsk.exe) in Windows XP, Service Pack 2.
* Corrected a bug in the boot time defragmentation. PerfectDisk records the current time on shutdown and compares it to the system time at reboot. On Windows XP, Service Pack 2, the system time at reboot can be earlier then the system time at shutdown. Raxco was unaware that Microsoft was able to travel back in time.
* Some code segments were changed to be consistent with PerfectDisk Live.