If you want to resize your partitions, create a new partition to install another operating system without losing your data, you need a powerful disk partitioning utility like Partition Magic. If you don't want to pay for a commercial application, you can use QtParted, an open-source utility that comes with Knoppix.
Ok, but what is Knoppix? Knoppix is a Linux live CD based on Debian distribution. That means you don't have to install it on your system, you just burn it on a CD and boot from the CD.
After Knoppix boots (type knoppix at the boot prompt), start at the large letter K at bottom left. Select K | System | QTParted to launch the utility. The main window is split into left and right panes. The left lists any hard drives that QTParted detects. Click the drive you want to edit, and QTParted will scan it for partition information, displaying the details in the right pane.
You can resize the partitions (choose Resize options), create a new partition. The tool will write the changes to the drive only after you select File | Commit. After QTParted finished repartitioning your hard drive, click on the K menu, and select restart. Remove your Knoppix CD and that's all.
QtParted supports FAT32, NTFS, HFS, ext2, ext3 file systems.
You can download Knoppix from one of these mirrors.
Burn a Windows Live CD
System Recovery CD
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