I tried a different hard drive, thinking that would do the trick, and straight away the infection was on it, so if it was just the boot sector then how does that happen? Could this be on the BIOS? I've tried any way I can to flash the BIOS but without success just in case, my knowledge in this area isn't good though. It's a HP computer, by the way, and the backup disks aren't exactly useful.
The initial infection mentioned above installed a number of different viruses which my virus protection blocked or removed, eventually one persistent sys file was removed along with the registry entries linked to it (knabsce.sys, doesn't appear to be a known name). I thought that would be it but running RootRepeal revealed, and still reveals 'MBR Rootkit Detected!' on all volumes (the main drive, the backup D drive and an attached portable hard drive, this last one is one with all my data backups on and. if nothing else, this is one that I need to have clean so that I can access them). How it got there is probably from a downloaded utility that turned out to be infected. I had AVG running (full version) but it picked up only some of the viruses thrown at it at the time.
All of this has been posted from my laptop as the main computer is not now connected to the internet and pretty much in its factory state.
Anyway, after three days of trying to sort this myself, without success, I thought it was about time I asked someone who knows better what they are doing.
Attached are the files as requested -