Vaio laptop won't start

Hello,
OK heres the story,
I opened my press one day and a bottle of ketchup fell on my laptop destroying the screen. All was fine for a few years until the screen kept buggin me so I opened my laptop and removed the screen. I put it all back together, plugged it in to a external screen and..... it started all right, but with a blank external screen. I put the broken screen back in and it still doesn't work. I opened it and turned it on, I can see the fans start, then stop, i can hear the disk start spinning but then the whole thing just shuts off.
I honestly don't know what to do and I don't to buy a new motherboard because it is an old computer and i'd be better off buying a new one.

Thanks