Nope, no luck. It has kept freezing although, so far, it has mostly recovered on its own after about half an hour. Temperatures remain as above so I don't think they are the cause of all of this. Twice in the last few days it has not recovered spontaneously and has had to be rebooted. The Google SyncDoc "App Crash" notice on Event Viewer has not yet reappeared before any of the crashes.
Just to answer one other suggestion made a few days ago, the HDD is around 75% full so has 25% free space. The huge swings in free space of old seem no longer to be evident since a round of updates to Vista a couple (-ish) of months ago so the 25% free space is happily pretty much a constant nowadays.
I know that it's on its way out but I hope to achieve a planned escape from it at around Christmas. It would be great if it could be coaxed into surviving that long so ideas will be gratefully received and enthusiastically tested. Thank you.