Black Hole
May contain traces of nut
That's only advice suitable for custom-firmware haters - 1.01.09 is only a stop-gap. The best instructions are here: Quick Guide to Disk Recovery (click)Apologies - that wasn't very clear. I meant that I downloaded Humax firmware 1.01.09 as per the instructions on this site for dealing with the destructive delete problem and tried several times to install it. I tried both USB ports several times but it would not install. The Humax remains in "delete" mode, although nothing has actually been deleted. I can watch all of the recordings. I can also watch live tv. What I cannot do is get into the Settings section to format the disc or retune the stations because it is greyed out. Which is why I asked if replacing the hard disc would solve the problem (the destructive delete problem, not the firmware installation)
However, if you cannot update firmware by USB you are stuck. The usual reason for this is an unsuitable UPD (USB Pen Drive). Try another, and keep trying until you find one that works (2GB or smaller by preference). Ensure you are following the instructions given in the link above to the letter.
Yes, you could just replace the disk, but you still need to sort out your inability to update firmware.