Why do you need to shrink C drive?
Shrinking volume from C drive takes fully advantages of a hard disk that does not
using its all space. For example, you have a 200GB hard drive with only C drive
partitioned and there are 50GB in size has been used. You may want to shrink C drive
to 100GB for system files and make a new partition for personal data or new released
system with the generated space.
Some users want to shrink C drive and extend D drive with the redundant space. This
may result from unreasonable partition layout when they first partition the hard
drive, which may make hard drive management harder.
Anyway, no matter what factor leads you to shrink the system drive, the most
important thing is to find out how to do this. Following parts will discuss three
methods about shrinking C drive in Windows.
Shrink C Drive with Windows Built-in Tools
Here in this tutorial, it will take shrink C drive partition Windows 7 for example.
However, before you start, clean up some of the crap first. For instance, empty the
recycle bin and delete useless files on the C drive. Next, create a system image
for your computer. These methods won’t cause data loss but you cannot be more
careful in dealing with system and data.
Disk Management: Shrink C Drive in GUI
Firstly, right-click "Computer"-> "Manage"->
double click "Disk Management" and right-click the C drive, select "Shrink
Partition". It will query volume for available shrink space.

Secondly, type in the amount of space that you want to shrink by or
click the up and down arrows behind the box (no more than 37152 MB).

Finally, you will see the unallocated space next to C drive.

Shrink C Drive Command Line
Diskpart is one of the built-in partition tools in Windows, which is an embedded
product that needs to be used under Command Prompt. Press +
key at the same time to start Run box.
Cannot Shrink C Drive?
When shrink C partition with Disk Management, you are likely to encounter one
confusing situation. For example, you have 909 GB on your C drive. However, when you
plan to shrink this partition only to find the available space is only 297 MB
according to the querying results. While at the top of the screen, it indicates that
C drive has 472 GB of free space. What is wrong?
Well, the answer is the size of the available shrink space can be restricted by the
amount of space currently allocated to on the hard drive for the virtual
memory page file, system protection maximum storage space
size, and hibernation files. The location of the files
on the hard drive plays a big part here because these files are marked as unmovable.
Disk Management is unable to relocate them. If these files are located in the middle
of the total amount of free space on the disk, then only the free space on the other
side (usually its right side) can be used to create a new partition. And the same
situation like before appears. What’s worse, even though there are no obstructive
unmovable files, you can only shrink half space of the total amount with Disk
Management.
Best Free Software to Shrink C Drive
It is time to turn to third-party partition manager when Windows snap-in programs
won’t work. You can try AOMEI Partition
Assistant Standard (free) which can relocate those files without
damaging any of them. It is an all-around and comprehensive application that
integrates simple-to-handle options for disk and partition management. The Standard
edition is a freeware that has earned good reputation among worldwide users. It can
also be used to shrink C drive in VM machine.
To shrink C drive in Windows Server like Server 2003, Server 2008, Server 2012,
Server 2016, etc, you can refer to AOMEI
Partition Assistant Server edition.
How to Shrink C Drive beyond Limit via AOMEI Partition Assistant?
Step1. Download,
install and run this software. Right-click C drive and select "Resize Partition"
or select this option in the left panel (you can see the free space of C drive is
29.87 GB).

Step2. Type in the amount of space or drag the double-headed arrow
to resize.

Step3. A gray unallocated space just behind C drive, click "Apply"
to execute operations.

Notes:
- In the window "Pending Operations", you need to confirm these
operations and click "Proceed".
- The C drive is in using, so the program will finish these operations in restart
mode automatically.

Tips: To shrink C drive and extend D drive, you can select "Merge
Partitions" to add the generated unallocated space to D drive. This method also
applies to shrink D drive and expand C.
To sum up, AOMEI Partition Assistant can help you do the task that the built-in tool
can’t. Another way to make use of space in C drive is create partition in C drive
directly. For more information, see how to
partition C drive. Except for shrinking C drive more than half space, you
can use it to move partition, merge
partitions, copy disk, migrate OS from MBR disk to MBR SSD or disk, and more
advanced function, command line partition.