I looked into ripping my 2 yr old SAGEM PVR HDD at some length with Googling. Also discussed with other SAGEM owners.
Someone did identify that the HDD has 5 non standard partitions. But then had to stop his own investigations for time reasons.
The overall conclusion was that nobody could be found who had solved it.
SAGEM units have (somewhat flaky) USB sockets and it is possible to export recordings, but only one at a time at about quarter speed. ie 30mins for a 2hr film. Depends on bitrate of course.
It is not possible to transfer avi or ts or mpg files back into the unit unless it previously exported them.
Other manufacturers are different. Very latest models have ethernet connection and are much more flexible. They seem to be £200-300.
Check your unit in specialised forums
eg click here