If we want to change partition size by using professional partition magic, we should download and install it to computer at first. After installation, run it to enter its main interface. In the main interface, please select the partition whose size needs changing and click “Move/Resize Partition” button to get the next interface like the left screenshot shows. In this interface, we can change partition size in Windows through dragging triangles on both sides of partition handle or inputting exact value to corresponding textbox. After that, click “OK” button to go back to main interface. From the main interface, we can see preview effect. If size of selected partition has been changed, we should click “Apply” button to apply all changes to computer. After that, professional partition magic helps change partition size in Windows successfully.