Hi this laptop worked perfectly up until a few weeks ago now it switches itself off after about 5 min you can't even sign in, I heard that sometimes this could mean it needs new thermal paste but when I opened it up it has no thermal paste at all, I've cleaned it all out so theres no dust, the fan is working fine and all vents are clear, please help as I can't afford a new laptop and I need this one working.

Thanks
Dave

Dave, September 2011

Update from above thanks for your answer I have checked and the fan as everything else is dust free.
On advise from someone else I deleted the operating system and rebooted with Ubuntu the strange thing is that although the laptop stays on now it's so slow it's ridiculous it takes a full 10 min to go from pressing the on button to Ubuntu being fully loaded and working then anything I press takes 5 min to actually do anything.

Dave, September 2011

NO thermal paste at all? It's strange.
Anyway, you don't need new thermal paste if you don't actualy remove the heat sink.
The only normal concern is dust buildup and fan failure.
Check for dust under the fan. It's the worst place it can be.

Make sure that the heat sink is properly seated with a very thin layer of thermal paste between it and the CPU.
The thermal compound purpose is to fill any eventual air gap between the CPU and the heat sink. It's less conductive than direct metal-metal contact, but much beter than air.

The heat sink should be held in place over the CPU by a metallic clip or some other mean, like bolt like rods going through the mother board. It MUST rest flat and firmly on top of the CPU.

Electro, September 2011