My old pavillion zt1231s will try to start and may even get past logging in but within a few seconds shuts down. the shut down is instantaneous. further start attempts usually result in faster shut down not even reaching the log on screen. It looks like overheating but the system does not run long enough to get hot. Tried starting whilst spraying the processor and heat pipe with freezer, to no avail. I have a new, secondhand, processor coming just in case it is the processor. Any one got any suggestons for possible causes.