How to do the installation of win10 actually used 30G? Win10 C disk space is insufficient solution

win10 claims that the system disk space is less than the previous version, how can it happen that win10 just took up 30G?

1, win10 itself does not occupy a large disk space, below 20G, but the upgrade will cause the previous preview version of the residue, especially the recent versions have changed a lot, basically a new installation, so will The windows.old directory is automatically generated for rollback.

2, this directory is also about 10G, forcibly use the right button to delete, will report the system permissions are insufficient, can not be deleted, how to delete it?

3. In my computer, right click on the drive letter of the directory, such as Xiaobian is on the C drive, select the bottom line in the pop-up menu <Properties>
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4. Select the <General> tab in the pop-up menu, and then select <Disk Cleanup>

5 as shown below. The system will automatically scan and collect. Cleared space, but the system does not clear the system file by default. You need to select <Clean System File> in the pop-up menu, as shown in the red circle below.

6, the system will calculate the space again. This time, the old system file will be calculated. Check the <previously installed windows> checkbox, there is 11G. If you want to clean it again, you can also select the , which is also close to 2G. Then click OK.

7, the system will show that the file on the C drive is being cleaned up, so that after cleaning, the root disk can get nearly 13G more space, which is really slim.