I've now looked at 9 of this series with a variety of chip and HD specs. All share the same problem - random screen freeze-up, no operation of keyboard, mousepad or mouse, often, but not always followed by involuntary machine switch off.
Because they are all well out of warranty, no help has been available from HP. All the geek sites have provided useful info, from hardware checks - Speedfan etc., updating drivers for everything including the AMD graphics cards, cleaning out dust, but none have provided a cure.
Both the 500 series and b27SA models are involved.
Has HP ever put out any advisories other than what I've already done?
Joxter (TIA)