Ok here is a write up of my experiences from the perspective of an amateur with a screwdriver!
I decided to replace my drive after getting "this channel is scrambled or unavailable message while watching recordings. More noticeably when the hard drive was recording other programs. Also a sector count warning via Webif got to over 2000 bad sections so it was time to act and save my 550gb of recordings.
1/ First i ordered a drive as recommended by MartinLiddle as being a like for like replacement-
http://www.ebuyer.com/337318-seagate-1tb-pipeline-internal-hard-drive-st1000vm002
2/ I attempted to get my recordings off the old drive. I started off connecting over FTP using WiFI and Filezilla but the process was very very slow. Now this may have been my connection but it was too slow for me so abandoned that idea. Second attempt was using a wired connection straight to my PC but i was unable to establish any connection at all so gave up. My IT dept offered to transfer the files for me at that stage so i cracked on with the install.
3/ Opened the box removing 3 screws, a further 4 screws securing the Drive holder to the motherboard, and a further 4 screws keeping the Drive firmly in the drive holder were removed. The old drive was noticeably heavier than the new one! I was quick frankly amazed at the temperature of the old drive, it was very very hot...
4/ The new drive was screwed into place and the box put back together.
5/ I restarted the Humax. It immediately came up with a "this disk needs formatting" screen. I then used a few button presses to initiate the format, and once this was done i could see that it had worked perfectly. It is worth noting that it recognised the 1tb drive but only gave me about 950 actual gb for storage, the rest i assume taken up by "working" files.
6/ Now i looked to see the damage in terms of settings. To my joy all my favorite channel lists and recording schedule was intact. Good so far.
7/ Next i tried the Webif. This didnt work initially but after a short period of time i was able to connect. I have no idea why this was. Once a connection was established i noted that i had to reinstall all the upgrades & additional packages again, which i did. Things like portal xtra1, mongoose, etc.
8/ I connected to the remote scheduling portal and could see that my new drive was not being seen. So in the settings page i deleted my old machine details and went back into the Webif. Using the settings page that carries the details to register for remote scheduling i entered my email details again and the new data uploaded overnight. So all good so far, just the recordings to deal with.
9/ Disassembled my box again and took the 2 drives to work. My IT dept were unable to help me as the Humax drives were in a native format ( maybe that could have helped more but in my case they didnt. The drives were not recognised and so nothing could be copied over). However they gave me a USB caddy to try and move stuff across myself.
10/ So back home, Humax reassembled, i connect the old drive in the USB caddy, to the front of the Humax via the USB port. Starting to transfer files across it was still a bit slow but overnight it transferred approx 50% of the recordings. It probably would have done more if not all but i failed to remember i had a shutdown/ restart scheduled in the early hours and this cut my copying connection.
11/ Second evening of copying and all is good. Tonight it copied a lot faster and my recordings are now all complete before bedtime! Little one is happy to have Horrid Henry back to watch and i have my Minder !!!
Footnote- Unfortunately i still have an issue now with my wireless. The wifi box is greyed out and says no connection, even though i have the wifi dongle plugged in the back. This worked when i assembled the box the first time so i fear i may have inadvertantly damaged the connection somehow on the back which is stopping this from working. If anyone has any ideas please let me know.....