My hp 430 notebook pc shut down automatically after I use it for a few minutes. I've change the thermal paste and clean the fan.but the problem persist.

Clean the cooling sistem and change the thermal paste

#1 on the list for this is shut down from over heat due to CPU fan not running or CPU overheat. Check to see if your CPU fan is turning on when your system is powering up. If its not.. thats your problem (get a new fan)... Even if it is it could mean the fan is not properly contacting the CPU with thermal paste. If this is the first time you\'ve powered the system up, your next step is to go out and get some thermal paste and put it under the CPU fan, if you\'ve been running the system and this problem just cropped up.. skip the thermal paste, its already there. #2 Next possibility is BIOs power settings are incompatible with your hardware. For example the frequency on the CPU is set higher then it can operate and its over heating. Some systems will automatically shut down and restart with default settings others you have to get into and set to default. can you get into BIOS? Can you reset your BIOS settings to defaults? Check your mother board manual. #3 A compenent is shorting out your system and needs to be replaced. Is the system posting prior to shutdown (beeping once on start up?) If its beeping more then once that means something else and you should read your manual. If its not beeping then its a short somewhere and you can bet you have a bad part in the system. To identify which part it is you can either disconnect things (RAM, Drives, vid card, PCI cards,ect) one at a time, attempting to start the system after each one or you can take everything but the bare bones out and try to start it. I usually take all the RAM out but one stick and start by testing them. Your RAM is the most likely place for a problem in this situation. #4 If you\'ve striped it down and it still can\'t get a boot (with no post beep). You need to replace the mother board.

I think it is time for a new notebook

Clean the fan of dust. Change thermal paste. Check if laptop is overheating.

The laptop must be taken apart and cleaned, remove fan and heatsink get a can of compressed air attach straw, now give a good few blasts to the heatsink fins to remove the dirt including fan, Next get rubbing alcohol and clean the old thermal paste from the processor and heatsink, when finished apply fresh thermal compound to both items and assemble.

I think you're right. Sounds as if the system is overheating. Check the fan is working. If it is, you will probably need to open the case and clean out all the vents & the fan. Remove the heatsink, clean off old thermal paste and renew before replacing the heatsink

It could be more than just Canned Air. It could be that the Thermal Paste that helps keep the CPU cool is dried up or not thick enough. Try these guys at: http://www.generalsystemsconsulting.com

They will fix it and ship it back Fedex or UPS at a very economical price. Ge a quote at your local shops then contact them

probably the cpu or gpu (from graphic card) is overheated during intense work

Computer shutting off after a few seconds to a few minutes

This sounds like an auto shut-off signal given by the processor because of a possible over-heating issue. This usually happens when the laptop has been run for an extended time without having the dust, dirt and debris cleaned from its cooling vents and grills. After time, the thermal paste on the processor bakes under the extreme heat and starts to flake off and lose its efficiency at cooling the processor.
Get a few cans of compressed air that you would buy at an office supply store and using short bursts, blow out the dust and dirt from all the ventilation grills and vents first, make sure the laptop is powered down and battery removed. Then, open all the compartments and clean them out as well including the cd/dvd tray. There is a small black hole on the dvd bezel, just stick an open paperclip in it and it will pop the tray open. Blow a good blast in there to clean the dvd player.
There is the possibility that the thermal paste will have to be replaced, that means you need to gain access to the heatsink and remove from the processor, clean all the old thermal paste from it and apply a small thin layer of new paste to the top of the processor and replace the heatsink, securing it evenly with the attached screws.

Your CPU is likely overheating. Very likely the thermal conducting material between the CPU chip and the heatsink may have shrunk and now impeades the thermal transfer.
You may need to remove the heatsink and put new thermal paste and perhaps copper shim to restore the thermal contact to the heatsink.