This seems too long unless the disk drive is very dodgy.
Assuming you've aborted the format, you might try again. If the disk format still fails, your pre-owned HDR Fox may be slightly foxed. Installing the Custom Firmware would allow you to diagnose the drive on the box. Otherwise you'd have to remove the disk and connect it to a PC, eg via a SATA disk caddy.
I think you might be right. I switched it off and powered it back on again. I did a factory reset and all the recordings were still there but previously when I looked they had disappeared. The clicking noise has come back but for the past 7 hours while it was supposedly formatting it had disappeared. It was freezing in places as well so I switched it off into standby mode. I waited for it to power down but it kept on whirring so in the end I had to unplug it.