Turn on the computer and start the operating system that you do not plan to remove. Click on "My computer" and browse to the local drive where you installed OS unnecessary. Click the right mouse button on the icon of this section. Select "Format".
In the menu that opens, specify the format of the file system and cluster size that will be assigned to the partition after the formatting process. Click "Start" and confirm to start the disk cleanup.
As you can see, this method will erase the system partition of hard drive. If you want to delete only the operating system files, do it manually. Open the list of existing partitions. Look at the top of the work window of the tab "tools" and expand it. Select "folder Options". Open the View tab and check the box next to "Show hidden files, folders, and drives". Click OK to save the new settings.
Open local disk, which is unnecessary to copy operating system. Remove from this section the following folders: Program Files, programData, Temp, Windows, and Users. Delete all files located in the root directory of that partition, except those that you need. Most likely, you will have to confirm the deletion of specific files. This process can take a long time.
If you want to save time, simply copy all the important files on another partition of the hard drive and format the unnecessary volume.
Now disable the download of the remote operating system. Open control panel and navigate to "System and security". Now select "advanced system settings" located in the menu "System". Click "Settings" in menu "startup and recovery". Uncheck "Display list of operating systems". Then restart the computer.