Hairyloon

That is certainly how I would have designed it. This would not be the first thing to make me think it is not well designed, though it is certainly the worst. I don't know what has happened. My guess is that having filled the disk, it has reset and "wiped" the disk. If that is what happened, then it is a really stupid design, but I can't think of another explanation. But, unless you take a considerable effort to do so, when a disk is "wiped", it doesn't actually destroy the data, though, as you say, if it has been written over, it becomes very difficult to recover. Maybe I am wrong, and it has just had a very busy few days that has filled up the disk. Either way, I still want to find an alternative means of accessing it, as the interface they have provided is rubbish.

Yes, I knew that. The disk can store several weeks worth, if it has only overwritten a couple of days, there is a good chance the relevant data is still there. The issue is getting a computer to recognise it.

A while back I bought a CCTV system for my house. It is nearly brilliant, but the bit by which it misses makes it rubbish. The only identifying feature is the product number: DVR-MJ14 A few days back my lodger had an altercation with some thieves. I've been away, so he has been looking forward to viewing the footage, but it only has film from the past couple of days. My guess is that the disk ran out and it has started overwriting, which would mean that the data is still on it, but I can't think how to access it. It plugs into the computer via USB. The disk has an unknown filesystem and it comes with its own software to view it. Any ideas?

I've got one of these as well. It falls just short of being brilliant... in the same way you might fall just short of leaping a deep ravine. If you're still stumped, PM me your email address and I'll send you the software that came with mine.