If you are making the laptop disassembly for the first time in your life, pay attention to this tutorial — First time repairing.
The article listed the basic precautions necessary tools to disassemble the laptop, as well as recommendations for disassembly and cleaning.
This video shows Dell Latitude 120L D620, D630 disassembling and fan cleaning.
If your laptop is overheating during operation and sharply turning off, this most likely is overheating of the cooling system. The reason for this is the accumulation of dust on the radiator. If not clean the cooling system in a timely manner, it may cause damage to the laptop. You can eliminate this problem by repeating the procedures shown in the video below.
This information is provided for informational purposes only. We accept no liability for damage caused to your device while following the video instructions. Also note that if your laptop or any other device is still under warranty period, then in the process of dismantling the guarantee may be canceled because traces remain after disassembly and it violates the terms of the warranty period. Before disassembling, make sure that the warranty on your laptop has been over.