Manipulating the size of a Windows filesystem when using Parallels on Mac OS X

Users of Parallels on Mac OS X are probably already familiar with the existence of the tools, provided by Parallels, to increase the size of a disk image. However, increasing the size using the Parallels Image Tool merely creates additional empty space on your Windows disk image - it doesn't actually increase the size of your Windows drive.

Having created this extra space the simple option is to start Windows and use the Windows tools to create an additional partition in this new space, then mount it as a drive (e.g. D:). However, what if you want to extend the size of your original C: drive? You can't do that in Windows directly, not least because you just booted from it, but even leaving that aside you can't. Partition Magic won't work under Parallels either. You could, of course, completely reinstall Windows but that would mean losing everything and having to reinstall and restore from backups. Clearly you need a method which will retain the existing disk.

Linux to the rescue in the form of GParted. GParted is a bootable disk image (.ISO) which amounts to a Graphic Partition Editor. It runs under Linux, so it works well under Parallels. It can handle a wide variety of partition types and file systems, including FAT16, FAT32, NTFS for Windows users, Ext2 and 3, ReiserFS and more for Linux.

To do the job at hand, download GParted and leave the ISO file as it was downloaded. Edit your Parallels VM machine to boot from a CD (under the Boot tab in the Options section). Next go to the CD section and select the disk image for GParted that you just downloaded.

Now start Parallels in the usual way and it will boot in to the GParted system. You may need to turn off Intel VT-x support (on the Advanced tab of the Options section) in order to get it to boot properly.

Go through the startup of GParted - all the defaults are fine. Finally you should see your partition map and your empty space. Just click the C: drive then the Resize/Move button on the menu bar. Increase the size of your disk as required. Once you're happy with it, choose Apply All Operations on the Edit menu. Let that complete - it will only take a couple of minutes.

Stop your Parallels VM, change the boot order back to hard disk first and let it start up. Windows will come up with a blue check disk screen. Once that has completed (again, in a few minutes) let it reboot and the job is done.

If you need a very detailed step by step set of instructions, try here.