How to increase C disk space in Win7 system
First of all, download a section assistant on the Internet, such as the Professional edition of the Section Assistant in the picture.
When opened, click the Extended Partition Wizard in the Section Assistant interface.
If you want to enlarge the size of the C disk, select "Extend System Partition", and then click "Select the partition you want to extend" to expand the remaining letter.
Then select the disk to split, if you want to space from D disk to C disk, then select D disk.
Set the size of the C disk extension, you can drag the slider or enter it in the window.
After executing the pop-up prompt window, click Yes to go to the next step.
Wait for the partition extension to complete.