Huge hidden file in system drive

I made an image backup of my system drive to another separate drive (E:\). Since then, although there is a "WindowsImageBackup" folder on E:\ there is also a huge hidden file on C:\, my system drive. 71GB of a 100GB drive!!
It is so large there is little room left to install anything else. How can I delete a 'hidden' file? Is it part of the WindowsImageBackup? Will it go if I delete the "WindowsImageBackup" folder?
I'm so cheesed off with it I'm thinking about re-installing, and I only did so 10 days ago. Something must be wrong as I cannot even restore to the point before the image backup.
The little niggles with Windows 7 are beginning to mount up!

Cannot see it even after following your instructions.
I used windows' own create a system image from the backup and restore your files part of the system and security section of the control panel. There was opportunity to select place but not size (Which didn't surprise me as it would depend on c:\ size, would it not?)

Further to my previous post here is a screenshot of what WinDirStat is showing me.

The yellow area is the culprit, no name, 'unknown' is how WindirStat calls it.
What, why and how: did it appear, and can I get rid of it without re-installing.

It's curious. WindowsImageBackup is an explicitly named folder as you know. It does keep some small information in System Volume Information.

You may want to try "Partition Wizard" of all things. It has a "partition Explorer" which let's you explore all sorts of places. Failing that try "Search Everything".

Do you use hibernation? Might be the hiberfil.sys. Open the command prompt as admin, then type the followinh:

powercfg -h off

Hit Enter. This'll disable hibernation and also delete the hiberfil.

Unfortunately I don't think "Show Hidden files ,folders, or drives" gives you easy access to everything.