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Like Windows 7, Windows 8 built-in Disk Management has ability to shrink volume and extend volume. Just right click on "My Computer", choose "Manage", and you will get a popup window, choose "Disk Management" in left navigation bar. And then, your hard disk condition will show.
Then you need to right click on the partition which you want to shrink, and choose "Shrink Volume", then type a number how large space you want to free up.
When there is some unallocated space next to the system partition that you want to extend and right click the system partition that you want to extend, choose "Extend Volume", and type the number of that unallocated space. Then the Windows 8 partition resize is done.
Although there is some improvement of Disk Management Tool in Windows 8, but it still has many limitations in partition management. Because some advanced partition management in Windows 8 is still unavailable when you find your system partition is out of space which will be in red as below:
In this condition, you may want to shrink volume E: and extend system partition for Windows 8. After shrinking volume E:, there is some unallocated space next to it. And then right click the system partition, you find that "Extend Volume" option is grayed out. You are right, Windows 8 built-in Disk Management can only extend volume when there is some unallocated space behind it, otherwise, the "Extend Volume" option is not available. Because Windows 8 built-in Disk Management doesn't provide "Move partiton" feature, so you have to seek Windows 8 partition magic alternative. EaseUS Partition Master Free Edition, a comprehensive free hard disk partition manager and system optimization software for Windows-based administration, works well with Windows 8.
1. Download EaseUS Partition Master Free Edition and install it. After that, launch EaseUS Partition Master.
2. Right click the D: partition that you want to carve up free space for the C: drive on the disk map, and choose "Resize/Move partition".
3. Position the mouse pointer on the left partition handle. Drag the handle to the partition size you want when the mouse pointer changes to a double-headed arrow.
4. Now you get free space right behind system partition (C drive). Position the mouse pointer on the right partition handle. Drag the handle to cover all free space until the handle can't move when the mouse pointer changes to a double-headed arrow.
Tips: Sometime the unallocated space is on the left of the partition you want to extend, just drag the left partition handle leftwards to the size you want.
5. If you are satisfied with the operation you make, you will see the operations you do in Pending operations. Just click "Apply". You will have a bigger C drive.