How to Add Unallocated Space to C Drive? 

This video is about how to add unallocated space to C drive in Windows 10 without deleting existing partitions or files.
Usually, there are two options we can do with the unallocated space. Firstly, we can create a new partition by right-clicking on the unallocated space and selecting New Simple Volume. Secondly, we can merge the unallocated space with the C drive. This is exactly what we want to do, and we think many people would also like to do this because they might be running out of space on the C drive. But there is a problem, when we right-click on the C drive, the Extend Volume option might be greyed out. That’s because the criteria for Windows Disk Management to be able to add the unallocated space to an existing partition is that the unallocated space needs to follow that partition. If not, then you will need third-party tools to move the partitions around.
Here are steps to merge unallocated space to C drive without deleting any data:
Step 1. open up DiskGenius Free Edition (www.diskgenius..., right-click on the unallocated space, choose “Add Free Space To”, and then choose C drive.
Step 2. Please read notes carefully. Then click OK. A reboot is required when changing the size of the system partition.
Step 3. Click OK, and the computer will reboot into Windows PE mode to finish merging the space with C drive.
Step 4. Once all operations are successfully completed, the program will automatically restart the computer and boot into Windows again.