DVD-recorder HDD-formatting

[uno]

I have a Sharp DVD-recorder DV-HR480S since 4 years. I have noted that during the years the 250GB HDD will record less hours than 4 years ago. In SP it should be able to record about 105 hours. However today it can only record less than 40 hours in SP. I am about to empty the HDD in order to format it, to see if it helps. Is it necessary for DVD-recorders to format the HDD? Or is there something else that should be done to maximize the HDD? I cannot find any solution in the manual.

[handyguy]

My Panasonic recorder has a format option in the menu does yours? You can't defrag these things, but you should be able to format.

[samijubal]

Have you tried resetting the recorder? You should be able to do that without losing what's on the HDD. Almost everything digital needs reset somewhere down the line.

[uno]

There is the option of formatting which I now have done. The problem is that I had to remove everything I wanted to save. I did put it on DVD-RW-discs. The formatting helped and took some seconds. Suddenly there was 107 hours in SP i.s.o. 36 hours before formatting.
Also I have a reset button but that does not change this error.