First of all, according to Microsoft's related documents and some examples, the use of system disk space by Windows is amazing.

According to Microsoft's suggestion, the initial hard disk space of Windows 7 devices should not be a little 16GB, and ideally, it needs 20~35GB of free space to use all the additional functions of the system.

In addition, some operations you don't know will also consume a lot of system disk space. For example, installing some huge applications (which may not be displayed in the installer) and updating Windows Update can easily consume several GB of space.

As for the system image on E disk, the folder named WindowsImageBackup is actually a redundant system backup created by Windows Backup. According to user settings, this program can back up system images and user files, and it is redundant in stages (that is, the old backup will always exist unless manually deleted). According to Microsoft documentation, this feature may consume 200GB of disk space.

Reference:

Windows.microsoft.com/zh-cn/windows7/products/system-requirements

Windows.microsoft.com/zh-cn/windows7/backup and recovery-frequently asked questions

Windows.microsoft.com/zh-cn/windows7/back up your program system settings and files.