Here i am giving u some tips follow them carefully
Tools You Need For Dismantling and Cleaning
1. Philips Screwdriver (M2.5 will do)
2. Flat Blade Screwdriver (usually a test pen)
3. A brush (about 1 inch or 2 cm wide would do it, not too big)
4. Hex Nutdrivers (about 5 mm)
5. Thermal Compound
I usually have 2 Philips screwdrivers, big one for more unscrewing force, small one for less screwing force (so that I don’t spoil the screws), then a test pen for prying up parts and a brush for cleaning.
For this guide, because disassembling the motherboard is necessary, that is why you’ll need a hex nutdriver. A pair of pliers could do the job perfectly as well.
Before You Start
Here are a few things you’ll need to do before you start disassembling your Dell Latitude D620.
1. Clear your Table
Ensure that you have plenty of space (1 meter square would be great) to put all the components so they won’t go missing or falling off the table.
2. Prepare a Small Container for Screws
Every single screws taken out from the laptop has their own job in keeping the computer intact. Don’t lose them.
3. Disconnect all the Cables & Components
It’s wise to disconnect all usb cables, pendrives, power cords.
4. Put Some Cloth or Thin Sponge Under the Laptop
To make sure that the rough table surface would not scratch your laptop.
5. Remove the Battery
To remove the battery from your Dell Latitude D620, unlock 2 of the latches and remove the battery out from the battery bay.
# Ground the Motherboard
When the battery is removed, simply ground the motherboard by pressing on the power button for a few seconds.
# Ground your Hands
Ground your hands by wearing a wrist grounding strap or touching an unpainted metal surface from time to time.