A large part of the system backup is the Windows.old folder, and its main content is the sum of the three main folders of the previous operating system Windows, program files and users. Windows.old generally depends on the size of the old system, but at least it will be above 10GB. The most important thing is that this folder is protected by the operating system every day. In general, it is difficult to remove. Next, we will use another method to recycle it.

2. Clear with one button

1) Open this pc first. Note that the available space of drive C is about 24.4 GB at this time;

2) Right-click drive C to select properties, then click the "Disk Cleanup" button next to it, and click "Clean System Files" in the pop-up dialog box;

3) The system starts to calculate the disk space available for release on disk C;

4) The results come out. We can see that in addition to the "previous Windows installation" occupying 1 1.4GB, there are 646MB "temporary Windows installation files", which add up to about 12GB of disk space, and there are some sporadic small files, which add up to about 12. This is basically the chief culprit of the sharp drop in C disk space;

5) After understanding, the rest of the work will be much easier. Check the files to be cleared (these two items are not selected by default and need to be manually checked by the user), and then click OK. You will be asked again later whether you want to delete these files? Click OK;

6) Take a look at the disk space occupation after cleaning. Is it a lot bigger in an instant?

PS: Sometimes the difference in disk space before and after cleaning may not match the file size to be cleaned. This is mainly because Win 10 will produce some temporary files in the running process, and the system update will also produce some garbage, which will cause the difference before and after cleaning and the size of the cleaned files is inconsistent, as long as the difference is not too big, there is no problem.