Boot it from a stand alone memory tester CD and do a stress diagnostic
test on the hardware. That way you can demonstrate if it is a hardware
error. My last Toshiba 17" laptop had an incredibly annoying
intermittent fault that meant it lost the keyboard and mouse after a
while. This could be worked around by plugging a USB one in, but the
only way to power it down was to physically remove the battery or let it
run out.
Either way made bootup tedious in the extreme. A Linux test disk also
failed the same way and eventually it became so unreliable the keyboard
would crash and die before you could alter bios settings.
--
Regards,
Martin Brown