If I put it in the Humax and it formatted it I would lose everything on the disk including the copy of Windows Vista I presume?
Yes... but if it offered to format and you declined, you wouldn't have erased anything and you would have proven the interface. The fly in the ointment is "only" being 80GB (large at the time), but I think the HDR-FOX will go down to 64GB (no promises). But the big question (which you have not stated) is whether the drive is SATA2. Knowing the make and model will help.
Is this any loss to me or to anyone else if I decide to sell it or give it away to a charity for instance?
No. A PC of that vintage would be much better off running a light version of Linux (google "lightweight linux"), and I very much doubt anybody would want it even as a gift.
Linux I don't really know where to start it would have to be a USB I don't have any disks apparently.
Do you mean the PC has no optical drive? Live Linuxes can run from USB
if your PC is able to boot from USB. That very much depends on the capabilities of the motherboard/chipset.
Let's not lose sight of the target here. The aim was simply to try to decide whether the HDD is the cause of the problem or something else, so that we know whether we're barking up the right tree. This seems like a lot of faffing about just to do that.
Taking up ML's offer of (I presume) a tested HDD would confirm, but be an unnecessary cost if it turns out the fault is elsewhere.
Reviewing your OP:
On the menu tree the data storage and recording settings are greyed out. I've done the formatting thing twice more just in case to no avail.
Please confirm:
Menu >> Settings >> System >> Data Storage
I took it to the same local tv repair shop but after trying and failing to fix it he said it must be a problem with the motherboard or firmware.
The question is what did they do to come to that conclusion. As we don't know, we have to take it with a pinch of salt.
To cut a long story short it's most likely a disk problem (I'm pretty much a newbie so don't know if it could be some other hardware problem but live tv and epg are working perfectly)
I don't think you can say that (live TV and EPG will work even if the HDD is disconnected). A fault in the services required by the HDD will also manifest as "a disk problem".
Your command line stuff says the operating system is unable to even detect a HDD connected, let alone format it, so if you are getting your format option from
Menu >> Settings >> Installation >> Factory Default (which also wipes your tuning etc), that's a case of the factory reset operation being too dumb to realise there isn't a HDD available, so it's a red herring.
Is it worth getting it to Richer Sounds which we bought it from or another tv repair place or even a computer repair shop?
Not Richer Sounds, no. They wouldn't know what to do with it. TV repair: also no. Maybe the answer is to take
just the HDD to a computer repair shop and ask them to test it, which is what I was trying to do in the first place. (Except computer repair shops won't be open until non-essential businesses can open again.)
Are you willing to take the HDD out and test it on a PC (under instruction)?