If you are using windows 10 so this allow you to backup system image backup and save previous versions of your file regularly. So this operating system has many backup features to protect system and files. If you want to delete windows image backup so follow these steps.
Go to setting >Update and Security > Backup > Go to backup and restore (open the old image backup tool) > click on Manage space.
Now you will see Mange windows backup disk space, you can click on view backup to select any of the image backup file to delete. Select and delete. [In the case of if you have previous image backup file]
After this you can also change the function of how windows manage the previous image backup. Then go to change setting and you will find two options: (a) Lets window manage the space used for backup history. (b) Keep only latest system image and minimize space used by backup. So here you can choose (b) options. I hope this method will definitely work.
I'm using Win 10 and can say that in order to do that, you should choose the Start→Control Panel.
Then under the System and Security heading, click the Back Up Your Computer link.
Click the Change Settings link.
Click the View Backups button.
If you want to delete a backup, click it once and then click Delete. ...
Click Close and then click X to close the Backup and Restore Center.