Your best option would probably be to open the case and pull the drive out, then connect it to your computer and see if you can access the files.
Page 65 of the user manual contains information about copying files from the HDD to USB storage.
Disc (CD-DA/CD-R/CD-RW, DVD+/-R,DVD+RW,DVD-RW) => HDD or USB
PTP USB is not available when you copy to USB
The broadcast signal can be recorded on HDD but copy feature is not supported
Also, on page 79:
This item incorporates copy protection that is protected by US patents and other intellectual property rights of Rovi Corporation. Reverse engineering and disassembly are prohibited
Proceed at your own risk...