The Short Version: A Boot Camp partition that had been removed left modifications that needed to be cleaned up. The solution was to boot from an install disc (Snow Leopard at the time) and run “Repair Disk”. It found errors and corrected them. I also repaired permissions (again) but I think running “Repair Disk” is what fixed the problem. I was then able to run a “Full Defrag” using iDefrag.
I recently decided to add a Windows partition to a Mac (OS X 10.6) system via Boot Camp. This was the second time. Windows had been previously installed and then removed. Unfortunately, every time I ran the Boot Camp Assistant to repartition the Mac I received the following error:
The disk cannot be partitioned because some files cannot be moved.
I tried running iDefrag in Full Defrag mode. That didn’t work. Next, I moved a large Parallels VM image to a USB drive, deleted the original, and then restored it. That also didn’t work. After reading some more suggestions I ran iDefrag again but this time selected the “Compact” option. It didn’t work.
Ultimately, I think the problem was caused by previously having a Boot Camp partition installed, which made some writes to the startup device that were not removed the first time the partition was removed.
What appears to have corrected the problem was to boot from a Snow Leopard install disc, open Disk Utility, and run the “Repair Disk” command. It did find errors and corrected them. After that completed I also repaired permissions, but I’ve done that from the OS previously and doubt it contributed to fixing the problem.
Once the disk was repaired I was able to successfully use Boot Camp Assistant to repartition the drive and install Windows.
Press Any Key 
This solution helped me too, I was moments away from wiping the whole drive and re-installing everything and I found this miracle post. This solved my problem like he has said. Thank you!
Thanks for letting me know. I don’t post very often nor do I get many hits. However, my posts tend to be solutions to specific problems and I try to save others the same amount of time and frustration I had to deal with.
Thank you so much! Worked perfectly! I did this in Lion using the lion repair utility, holding down Command-R during startup. Thanks again!
Verified. OSX Lion. Command-R on start up and run Repair Disk. Works for me. I tried iDefrag and it did not work. Time Machine backup was my next move but it seemed unnecessary. Simple Repair Disk works. Thanks! Looked all over the net for this solution.
Verified on lion as well. THANK YOU!!
fixed my problems as well!!!! THANK YOUUUU!!!!!!!!!!!!!!!
I wish I could KISS YOU. For those looking for a solution to this, I’m running a iMac with snow leopard, and yes, this WORKED!
I love you.