Well, I have my computer back. There is no need to go into detail other than to say that when I mess things up, I can do it with some aplomb. The good news out of all of this is that I've met a real gentleman of the computer world who has spent no considerable amount of his own time putting things right. A big thank you Kris and a special mention of thanks go to my fellow preparator Mark who put me on to him in the first place.
As for the computer itself, well it would appear that the fix is one of those that is hard to quantify. It may last ten hours, ten weeks or ten years - there is just no way of knowing. But Kris has set the system up with a few fail-safe options and with the addition of an external hard drive I can rest easy knowing that all my data is at least safe.
So since reliability is obviously going to be a problem (and I hate that feeling of wondering if it is going to crash at any time), then I have no option but to invest in a new system in the near future. I suppose it was due anyway since I've had the current set-up since 2003 - ancient by today's standards. I'll time the purchase to coincide with the release of Windows 7, a quantum leap better than Vista by all accounts. Mind you, from a personal point of view, it will have to go some to beat XP - by far the most stable OS since Windows was launched many moons ago.
So next up is another field diary entry - computer permitting!