Dell laptop powering off oddly

OK this is possibly the weirdest issue I have encountered yet.

The computer (DELL Studio 1555) just randomly powers completely off by itself regardless what type of power it is on, battery, cord, just cord, just battery. I've even tried different batteries (compatible ones).

So the issue is though that it doesn't do it 100%, in fact it only does it (after 5-6 tests now), after it has been put on once.


So first time in a few hours I'll switch it on, and it runs fine perfect, 35 degree cpu approx 50 degree gpu (which I believe is ok). Play games, run stress test and it doesn't switch off or do anything odd at all and temps stay fairly cool. So I switch it off through windows and this is where the problem starts.

As soon as I power it on again now, after about 10 seconds it just powers off, it will do that anywhere, in bios, windows loading screen (although if it makes it that far it dose a blue screen of death instead informing me of fatal error with nothing helpful). It will do this every time after this now as well until I leave it for another 2 hours or so.

So I have tested

1. Running it without the hard drive in (still happens)
2. Tested it with one stick of ram and the other out for both sticks (still happens).
3. Reapplied thermal paste on gpu, cpu (much cooler temps, but still happens).
4. Tested with just battery, just power cable (still happens).
5. Taken out CMOS battery, reset bios settings, tried resaving new sttings (still happens).
6. The CPU fan is defiantly running and blowing air out well, especially after cleaning it (still happens though).

Any ideas what this could be? Or why it is happening only after using it the first time? Why wouldn't it do it the first time if It was a fault...? PREASE HELPS :) Anything else I can test?

Best Regards

I meant that I took the HDD out and turned on the computer and it still did it.