Windows used to come with a built in Backup program that could be used to back up your files to a second disk drive, such as a USB disk. Windows 8 doesn't have this facility and instead it has File History. What you may not realise is the large amount of space that File History uses.
File History is set up in the Control Panel and it automatically backs up all your user files like documents, photos, music and so on (not the whole disk drive) to a second disk drive. Every hour is checks for changed files and saves them.
The question is, what happens if the disk that File History uses, such as a USB disk drive, is not available. This can happen if you use a laptop away from home or the office, or you simply don't switch on the USB drive or plug it in.
File History continues to back up files, but instead of saving them to the external drive, it saves them to the internal drive when it isn't available. So disk space on drive C: is used. How much though?
Go to the Start screen and type disk cleanup to open the search panel open the right. Click Clear disk space by deleting unnecessary files in the search results.
This opens Disk Clean-up. Select the disk drive to clean - drive C: - and afterwards it displays a list of files it can safely remove. Scroll down to the bottom of the list and you will see an item called User File History. This is the disk space being used to store backups of your files. It stores versions of files so if a file changes, it saves that version,. so as you edit files it continues to use up disk space. I haven't plugged in the external drive for a few days, so it is using 747MB of disk space.
If you really need the space, you could select the User File History and clean up the disk. However, you will lose any versions of files that are stored. When you next plug in the drive, it will back up the latest version, not the ones created while the drive was offline.
If at all possible, do not clean up the User File History. Leave it. Plug in the backup disk drive whenever you can and let File History automatically run. You can go to the Control Panel, open File History, and set it running straight away if you don't want to wait for the next scheduled backup.
After File history has backed up all the files you have created or modified since the last backup, the disk space that it was using is made free again. You can see this by running Disk Clean-up again. Here it is after running File History.
Notice that User file history is now zero with nothing to clean up. Disk space is only temporarily used and is then recovered, so it would only become a problem if you didn't plug in your backup drive for a month.
There's only so much Microsoft can do to get you to back up. The software is there, you just have to plug in the drive every now and then.