Windows backup hanging

I've tried on 3 occasions tonight to back up my files etc. Every time is whizzes through the first bit, gets to about 12/13% completion and seems to hang. Whilst it was in this state there was no HD activity light, and I checked task manager, processes, and the backup process was showing zero CPU usage and memory use was static.

Should I just leave it on overnight and hope it has completed by morning. Surely simple file copying from one drive to another shouldn't take so long ?

Further to the above are you doing a file/folder backup or an image.
You should be able to see a progress bar. But it sounds hung.

I was backing up to another drive on my machine, making a system image and file backup. I left it on overnight and this morning it still hadn't completed. It's now stuck at 57%.

How much data are you data are backing up.
If it is on the order of say 50GB total. Personally I would terminate the application/process. Something has gone wrong.

Again a personal perspective: I never combine (Windows) file/folder backup with imaging. I want separate control of both so I always select the "Let me choose option" and always have "include an image" deselected.
I use the make an image now option on the left of the "Backup & Restore" screen. This also lets you select any partition you like, not just the current default backup location.

You should determine if the problem is with windows imaging or the file/folder backup by doing them separately.
If Windows imaging is the problem and you can't work out the problem I suggest you move to Macrium Reflect free (I use both).