Laptop power cuts off

I am working on a laptop (HP ProBook) which the hard drive died. Power had gone out at my clients house. When the house power came back on he turned the laptop back on and it would not boot up. Error that the hard drive was corrupt. So I replaced the hard drive. Reinstalled Vista, and everything was working fine for about an hour and a half. Then the laptop just powered off. (not shut-down "“ power cut off) From past experience this is a sign of a clogged fan or the fan not working. I cleaned the vents and the fan. The fan is spinning. System still shuts down after an hour and a half (assuming because of overheating)
Any thoughts?

 

did you check the power supply unit. just to rule it out as the problem. More likely than not you are probably right about the overhating.

 

You mean the power cable box? It seams fine. If it is overheating...I don't understand why if the fan is running? Do you think replacing the fan would fix the problem?

 

I might have been wrong about the power supply. I have had the laptop on for 2 hours without the power cord, running on just the battery. No problems yet. Might just be the power supply. I did test the power supply and it is send correct voltage. Will post more tomorrow.

 

Just a thought do you have a way to test the power supply. It could be on its way out. Then think about the buying the fan. Is the fan definitely working.

 

Did you check it just hanging in the air or plugged in under a load?