1) Right-click the computer in the start menu, enter "Properties → Advanced System Settings → System Protection" in turn, and turn off the C drive restore function.

2) Right-click the computer again, click the "Manage" menu, and select "Disk Management" from the list on the left side of the computer management window. The partition status of the current hard disk will be listed graphically on the right side of the window.

3) Select drive C with the right mouse button and select "Compress Volume" in the pop-up menu (as shown below). The system will automatically calculate the compressible space later, and the specific information will be listed in the "Compression C" window that pops up.

4) It is recommended not to modify the value of "Input Compression Space", and only click the "Compression" button to reduce the maximum capacity. The space compressed from drive C will be named "Unallocated" partition.