My worst fears are realized. It seems reports of Mr L33t's demise have been greatly exaggerated. The poor fellow's not dead, only irreparably lobotomised. Which is worse. No reason to purchase any further upgrades 'cos everything's working just fine -- except the hard drive which has utterly and completely failed.
As I said, all my important data has been backed up on an external drive, though I've lost everything of value within the past month... sort of being in between backups. But my saved games are probably unrecoverable.
Bought a 1Tb replacement HDD but will have to reinstall everything all over again. Painful. I'll have to replay all my games too! Someone's going to be busy over the December hols.