Why it's not power up

Hi!

I have a toshiba laptop a105 which was working well until last night.I closed it normally and today tried to power it up.The power led shows blue when i hit the power button but nothing.I can't hear the fun spinning and the power light stays on.Nothing on the screen and not a sound to confirm that the laptop is booting.I opened it and found too many dust on the heatsink.Apllied to the cpu new thermal paste but nothing same thing happens.I tested the power jack,it gives 15volts to the motherboard.What could be the problem?Any help would be appreciated.Thanks!