Is my motherboard bad?

[usmc21]

I have a Toshiba A505-S6992 Satellite Laptop that under went some fan cleaning / reapplied thermal paste. It was working FINE before I did this, it just had overheating problems, which is why I reapplied thermal paste. After putting it back together and upon booting up, I can hear everything working.. cpu an spinning/hard drives thinking. And when I put my hand against the fan, it's running cool. Awesome... Unfortunately, the screen turns WHITE the moment I power up. Opened up the laptop again and double checked everything. Seems to be all connected/seated. So then I hooked it up to an external monitor via hdmi/vga.. still nothing... Then I took out the MOBO.. disconnected the main cable running to the laptop monitor. and then tried connecting the Mobo to an external monitor. Still no connection was established...

What other methods can I do to isolate the problem?
It sucks because everything was working fine before I did this. I just wanted it to run a little cooler.
I'm beginning to think its the mobo that crapped out on me.

 

[danny2000]

Did you also take out the cpu and reseat it again, and clean off old paste and re-apply again? I know that you did it once, but since you did everything else, I would do this again, if you did not already do it the 2nd time.

 

[danny2000]

Also, try and clear cmos.

 

[usmc21]

Also, try and clear cmos.

I reapplied thermal to the CPU and Nvidia graphics card.. twice.. using arctic silver alumina.

Where is the CMOS located on mobo?

 

[danny2000]

Disconnect any power source, battery, power cord, etc.
Press the power button to discharge any saved power in the system.

Open up the system andremove the coin cmos battery that is on the motherboard for about 10 minutes or so.