I've had the PC open, and the problem seems to be with the fan identified by number 2 in this diagram, and not the CPU cooler that I suspected. The small fan had stopped completely. I cleaned it up as best I could with a small brush, and it's working - intermittently. I might just decide to upgrade - A7V333 would be my mobo, with one of the new Athlons. What's the difference between the "normal" Athlons and the multi-processor Athlons - apart from the price?