Laptop motherboard dead?

[Aspiring techie]

I am currently attempting to fix my friend's laptop, an Hp G62 407DX. I took it completely apart to clean out the dust (this laptop overheats like crazy), and even reapplied the thermal paste on the CPU.

I put it back together, and tried to turn it on. I heard the optical drive make a sound or two, and the power and f12(airplane mode) lights turn on. The caps lock light blinks on and off in 1 second intervals. Nothing shows up on the screen. What I find strange is that the laptop didn't power down when I hit the power button, but it does power down when I hold it down for a few seconds.

Can you guys help me either confirm that it's dead, or figure out how to make it work.

Here's what I think may be wrong:
1. Electrostatic discharge. I wasn't wearing an anti-static wrist strap.
2. Solder joints on GPU or CPU became undone. I read that this laptop sometimes overheats so bad that the solder joints become fragile, so maybe I somehow broke a joint by taking the computer apart.

I would appreciate any ideas. I know a decent amount about tech stuff, so don't be afraid to be technical.

 

[Laptop_Nerd]

Hi,

Here are some troubleshooting suggestion that I can give that may help.
- When the laptop is on but without display try connecting an external monitor and see if you'll get any display from it.
- Next is to reseat the RAM's, remove them all for couple of seconds then put them back in making sure all RAM's are seated properly into each slot.
- I would it's the motherboard if both these will not help.
- But if ever you'll get a display from the external display you may still be in luck since it's the display that's faulty you may try to check the ribbon cable that connects it to the motherboard.

 

[Aspiring techie]

I tried an external display. No go.

I reseated the RAM and it worked!! Thanks a bunch!

Quick question: Why was it the RAM?

 

[Aspiring techie]

Also, I can't seem to be able to select your answer as the best answer. Can someone do that please?

 

[Aspiring techie]

One thing has come up since the computer was brought back to life. It only recognizes 1GB of memory. The laptop has 3GB equipped. I booted into Linux and still only 1 GB is recognized. The strange thing is, in BIOS all 3GB are recognized.

I reseated the RAM sticks and swapped which slot the sticks were in (a 2GB stick and a 1GB stick). No go. Does this mean that 1 RAM stick is dead?