...beyond the basic routines which I mentioned at the start more complex problems are generally best fixed by a full reinstall as the investigations and analysis involved would consume more time than the repair - and you can never be quite certain you've sorted it all.
Quite so. I've sometimes used days to find out the problem, but in the end a reinstall was needed. It would have been time saving to go for reinstall directly.
One of my favorite themes is, do partition your disk in at least two: one where you have your Windows plus some essential programs, could be like 80Gb; then, have your personal files, archive like, in another partition or perhaps, another disk, maybe even an external disk = USB. That way you can replace the engine of the car, without loosing the wheels - don't know how wise that sounds...
