Moved out of the Help section.
The Raxco site has a Support section which lists a number of Known Issues. Their Knowledgebase has at least three articles dealing with problems similar to the one you are having - see the list at http://www.raxco.com/support/technical/21/14
The KnowledgeBase article that probably deals with your problem is http://www.raxco.com/support/kb/823 - "When attempting to perform a boot time or offline defragmentation pass, I get a failed to open message, driver conflict message or Windows fails to start properly."
This article specifically notes a problem with a McAfee program (mfehidk.sys) and tells you what to do about it. The overall problem is that
3rd party products have drivers that open the drive for write access prior to PerfectDisk's boot time defrag being able to mount the drive for exclusive access. If the drive has been opened for write access, for safety reasons PerfectDisk will not perform the boot time defrag.
Please read the whole article, and follow the steps listed there.
If you still have the same problem after following those steps you should probably ask for advice in the Raxco forums, since you are more likely to get answers to any further questions about a Raxco product in their forum than you are here. The forum login is HERE.