Here is an article that i found that talks about the problem you are having and how to fix it!
Youâre busy trying to use the Bootcamp Assistant to install a bootcamp partition on your shiny Macbook, when suddenly youâre greeted with the dreaded fragmentation dialog of death:
So what does âThe disk cannot be partitioned because some files cannot be movedâ actually mean? I mean, Iâve got 25Gb free and I only want a 10Gb windows partition! The answer lies in fragmentation. OSX seems to want a contigious block of clean disk to write to, and fragments of your files are scattered across it.
I know what youâre thinking. âBut itâs a Mac. Iâve got this fancy file system that isnât prone to fragmentationâ. Yeah, yeah. Well, dude, the crushing news is that you can fix the problem by defragmenting your hard disk then trying again, so I guess OSX isnât as committed to defragmentation as you might suspect.
Iâm sure there are many ways to defrag an OSX hard disk. I chose to fork out 20 Euro and make the problem go away using iDefrag. There may well be open source/free alternative out there (feel free to comment if you know of any â useful for other googlers who come on by). iDefrag does its best work when itâs not defragging the boot disk, so youâll want to generate a bootable DVD to run it from. Fortunately it ships with the tool to generate that bootable DV for you.
iDefrag ships will a free product called âCoriolis CDMakerâ. Stick your Snow Leopard disk in the drive, run the CDMaker app, and it will get busy generating a bootable DVD for you with iDefrag as the autorun. Stick your bootable DVD in the drive, restart OSX, and hold down the âCâ key as the machine boots â and it will boot up your DVD and run iDefrag.
Defragging takes some time â mine took about 3 hours to run â but thatâs a lot less hassle than reformatting and restoring my entire drive. After the defrag I could happily run the Bootcamp Assistant without any âsome files cannot be movedâ drama.
Article from: http://blogs.bytecode.com.au/glen/2009/10/28/bootcamp-assistant-how-to-overcome- the-files-cannot-be-moved-issue.html