Ah yes, thank you, ozzy, for your info.....I got online on a chat with one Jandy of Microsoft, let him get in and, jeez, the amount of useless files that he killed was amazing....that took about forty minutes and he then set up a three stage scan and stepped back, leaving me to trigger stages 2 and 3. The pc ticked away for about a further 90 minutes, nothing adverse showing up, so maybe it's nailed.
Thanks for the link though and catalysing the change - so far so good.