Hi ewanbcn
About the only things you can do in a case like this swap parts one at a time if you have any available.
If you have two DIMMS, try them one at a time in case one is faulty. Anything that plugs in (CPU, power supply, etc.)
for which you have a known working one, plug it in. You could also try checking the BIOS to see if it contains any
settings that may be out of wack (overclocking?), and if it has that displays CPU temperature and voltages, check
that too.
Or you could just try tinypoodles idea.
This is not a base issue, moving to Off Topic.