URGENT : DVR Ganz admin password unknown

Hello,

I've lost the password of my DVR Ganz DR4HL. This device is not connected to any network and it contains some footage of a robbery. Police has been informed and is currently trying to catch the guy as I write these words. The problem is that I want to know how the guy has entered on my property to fix that.

I have 4 cameras connected to the DVR and the DVR is recording everything. I bought the DVR from a guy in China and it didn't require any password until there was a general electric failure. From this moment the DVR required a password to access to the admin session. I tried to call the guy in China but he forgot the input. So now I want to recover the password without deleting the files recorded.

One more thing, this DVR is NOT connected to any network but there is a USB port, I don't know much about hacking but I guess I could use this.

I hope you'll be able to help me quickly.

Cheers