Laptop wont come on

Hello,

i have a hp compaq nc6000, pp2090 series and from time to time, when i turn it on there is a blue light that comes on this i now know is an indicater light that shows if the wireless is switched on or not . but wen i turn it on all i get is the blue light coming on then the fan will kick in for a couple of seconds then goes off. i know it works as it does come on now and again but ive also noticed it freezes alot when left unnattended to the only way around it is when i play music an it stays on fine then its doin me head in an ur help wud be gratefully appreciated thanx