When we talk about "units" labeled C :, D:, and so on, we are actually talking about partitions, parts of the physical unit. Each hard drive used has at least one partition. You can shrink that partition and create new ones from the extra space. You will find this useful if you want to install more than one operating system, or if you really want to separate programs and data.
But first you have to take some precautions.
Step 1: Make a full backup of the entire device if you do not already have one. Disasters occur. (See our selections for best Windows backup software to get started.)
Step 2: Make sure you have enough free space on the existing partition to create the new one. The following items may be useful for clearing space:
You may also want to empty the Recycle Bin.
If you still do not have enough space, you can move files to an external device. When the partitioning is complete, you can move them back to a new partition.
Step 3: Open Windows Partition Utility. Windows comes with a pretty useful partition utility. It will probably serve your needs, and if it doesn't, you'll know soon enough. To open it, type partition in the search field, and then click Create and Format Hard Disk Partitions . (In Windows 8, type partitions ̵1; yes, you need s .
Step 4: Shrink the existing partition. Right-click the partition and select [19459009[ShrinkVolume]
Then wait, it may take a while Eventually, a dialog box will ask how much you want the partition to shrink. The default number is the maximum available.
GB free should be able to shrink it by anything less than 228 GB, but Disk Management may not allow you to shrink it anywhere near as much. If the program does not allow you to shrink the partition as much as you want, skip to the last paragraph. device may have 23 GB of free space, but Disk Management may only allow you to have 12 GB of it.  Let's assume Disk Management lets you shrink the partition sufficiently. If so, set the right size, click Shrink the button and follow the instructions.
Step 5: Create your new partition. When the size has changed, right-click on the physical unit's unallocated space and select Simple New Volume.
Then follow the guide.
Alternative: Use a third-party tool
If Disk Management cannot shrink the partition as far as you want, it is time to join a third-party program. I recommend EASEUS Partition Master Free. It's simple and, as the name implies, free. And it can shrink your partition until there is almost no empty space. However, when installing it, select the option Custom Install to avoid installing extra, unwanted programs.