If it happens on all the pcs there has to be a BIOS option, maybe not under power management, sometimes its under ACPI or advanced settings->ACPL (AC Power Loss).
If you provide your pc's model (I'm assuming they're the same one) I could help you searching in it's manual the correct option.
what number are you looking for, ??? from the mother board?
it has FSB 800 Prescott 800
ASRock Dual channel
Dual core dDR 400
written on it, i have looked ac power loss in the bios under ACPI,
Restore on A/C power loss [ Power off ] is the selected setting
in chipset configuration there is option for
Full reset if AC/power loss [ Auto ] i have tried to disable this setting by selecting disable then f10 to save changes, but every time i restart the computer it has reset to Auto by itself.