Failed to install Windows 10 anniversary update
Many users have tried to install the Anniversary Update for Windows 10, but some of them failed with an error “Not enough disk space for anniversary update”, while they actually have more than 20GB of free disk space on the system drive. Though Microsoft has not yet given a clear answer, there are some ways that may help you to fix the 0x80070070 error and successfully install Windows 10 Anniversary Update.
Workaround and possible solution
Instead of clicking on the Windows Update when you receive it, you can also use the Media Creation tool to help you get the Windows 10 anniversary update. You can download this tool directly from Microsoft’s website.
When the Anniversary Update fails, you can also download the Windows 10 (1607) ISO. Just double-click the file when it is downloaded to open and run the Setup to upgrade.
According to Microsoft, users need at least 16 GB of free space on C: drive in order to install the Anniversary Update. As you may know, Windows update will create a backup of your current system so you are able to restore to your system back if the update fails. If your system drive has stored many files, Windows needs more free space for this upgrade correspondingly. That is probably why you get the Windows Update not enough disk space error. You can delete some files on to free up more space with Disk Cleanup or extend system drive.
Extend system partition before anniversary update
In Windows 10/8/7, it has a built-in tool Disk Management that you can use to extend a partition when there is contiguous unallocated space right behind the partition which needs extending. However, in most of the cases, there is no unallocated space on the hard drive or it is not contiguous, resulting in Extend Volume grayed out. In that case, you can use third party software AOMEI Partition Assistant Standard to extend C: drive. It allows you to add unallocated space to any partition on the same hard drive.
Step 1. Download and run this freeware.
Step 2. If there is already unallocated space on the disk, you can skip to step 4. Right click on a partition which has enough free space, and select "Resize/Move partition".
Step 3. In a new pop-out window, drag the slider leftwards to shrink the partition and then there is unallocated space.
Step 4. Right click on the system partition and select “Merge Partition”. In a pop-out window, select C: drive and the unallocated space, and then click “OK” to continue.
Step 5. Then you can preview the partition layout after this operation. If no problem, click "Apply" to apply the changes.
This freeware also provides “Move Partition”, so you can move the unallocated space and then extend system partition. Generally speaking, after trying one or more of the methods, you should be able to install the update without receiving the not enough disk space for anniversary update error.