My Sony vaio laptop doesn't boot, but power on, fan on!

my sony vaio pcg-k33 wont boot up, although the green power light is on and the fans run. That is, when I press the power button, it makes the sound as though it's about to boot, but the screen is as black as when it was working properly and the fans and power lights are running. What's wrong with it? What should I do?
I have followed all the majorgeek malware protection instructions since last year and my laptop was well protected, so it couldn't be a malware issue. I had the motherboard and DC jack replaced for new this year, plus got a new battery and a new charger/adapter, so everything was new except the outer body (shell), the RAM and harddrive. Is this problem to do with the RAM or hard drive or other? Please help.

 

Maybe the onboard video chip is gone that's why the screen remains black.
Do you hear any POST beeps? Did the computer beep once when it was working?

 

"Do you hear any POST beeps? Did the computer beep once when it was working?"

RE: NO i DON'T HEAR ANY POST BEEPS. ON PRESSING THE POWER BUTTON TO SWITCH THE LAPTOP ON, IT MAKES A BRIEF SOUND COMING FROM THE SIDE WHERE THE CD DRIVE IS LOCATED (as though the cd player is getting into gear), THEN THERE'S SILENCE AND THE SCREEN IS STILL BLACK, POWER LIGHTS STILL ON, FANS RUNNING.

 

Hmm laptops can be tricky...

Have you tried booting with the dvd tray already ejected?

Also did you install any applications or programs the last time you used it?

Does it have a sleep type mode or suspend key or similar on the keyboard..

If your getting no display doesnt sound very promising if no video, could have damaged ram and video uses shared ram? on this model?...so no display.

Sounds like it might need a trip to the shop...esp if its still under warranty.

Good luck with this one guy.