I'd forgotten about it in the intervening year-and-a-bit.

I already had 'BIOS Upgrade' and 'Try Knoppix to see if it's some weird Windows issue' on my to-do list, but after reading some of the temperatures other people were getting, a new heatsink/fan is on the shopping list.

Or I'll just give up, swap it with my Duron 700, and see if he notices the difference :-)