Righto Steve, well ya gotta appreciate it can be almost anything, the
ol' psu leads the hardest life in a computer has it has to run and
deliver a good 'reasonable' ripple free DC to power all, the heat that
the CPU has to get shut off the power unit gotta deliver.

When I mentioned the fans being free I thought of a sticky CPU fan
causing the shut down to prevent thermal damage, not all CPU's are
protected this way though.

The guy spent all afternoon building this thing.... the mobo was
black, the copper tracks melted, the cpu knacked .... the screw driver
looked as if it had lost battle with a mig welder... "and he was
sick a parrot".

Davy