Windows – How to partition single drive without losing data in it for Windows 7

You can use /Applications/Utilities/Disk Utility.app for that. It allows non-destructive resizing of partitions. See for example this article on how to do this. Alternatively, you can use the diskutil command line tool, see here.

Although it's possible to resize without data loss, you should always have a backup at least of your more important data on that disk. Power outages and system crashes while reformatting a disk aren't fun.

Once your HFS+ partition's size is reduced, you can create a new partition in the empty space (though you cannot create NTFS partitions from OS X).

I'm guessing you want to shrink the existing partition and create a new one with the free space. In fact, instead of using gparted like John1024 said, you can use a built in Windows tool to do this. As long as you have 50GB of free space, it should work.

First you will need to shrink your existing partition to make room for the 50Gb partition you are going to be creating.

Open control panel and search for 'partition'. Click on 'Create and Format Hard Drive Partitions'. A Disk Management screen should pop up. Right click on the partition you want to resize and click "Shrink Volume." You now need to shrink it by 50 GB to make room for the new partition. 50 GB is 50000 MB, so enter 50000 MB as the amount to shrink by, then click shrink. EDIT: I should have mentioned, in this screen, you will be shown the available space. Do not shrink by 50000 MB unless you have that much free space.

Now your disk should have 50 GB of free space. Right click where it says "unallocated space" and click "new simple volume". A wizard will pop up that will guide you through the process. Once you are done with the wizard, you should have a new partition set up.