Resize Windows partition on a Mac without destroying data
GParted should make it possible (I haven't used it), see comments.
The best way (that I have successfully used) is to use a utility to
- Clone the Windows partition to an external drive (or just to the OS X partition if you have room (also keep in mind this is risky – it's good to have the full backup off the disk in question), using Winclone within OS X. It just creates an image file that you can move around to wherever you have space, until you do the restore.
- Erase the Windows partition (it's ok, because you have the clone)
- Create your new partition however large you want, using the Boot Camp utility within OS X
- Restore the Windows cloned image to the new, larger partition
- Use the utility to "expand to all free space"
Also, I would run a "disk check" on the Windows partition twice before creating the clone with winclone. Otherwise, restoring will most likely fail.
You can follow some of the steps from this question.
In this method, you don't need to save any image of your Windows partition at all. Just doing these 2 easy steps, you will be able to extend your Windows (system) partition.
-
Start your machine in Mac OS
1.1. Go -> Utilities -> Disk Utility
1.2. Click on your hard drive ID -> Partition (tab)
1.3. Shrink the Mac partition as much as you need
1.4. Click on "Apply" button
Now you have an unallocated space in your hard drive
-
Restart to Windows
2.1. Download the MiniTool Partition Wizard from this link. The Home version of this software is free for all users and you can download it from Download.com as well.
2.2. After installing and running Partition Wizard, click on the system partition of your Windows -> Move/Resize
2.3. Extend the system partition as much as you need, click on OK -> click on Apply You may be asked to restart your Windows.
Enjoy free fresh space on Windows!
GParted can resize NTFS partitions. It has a Live CD, but I have no idea if it works on Macs.
FWIW, extending a partition is simple. Shrinking is tricky.