Won't Turn On

I have a Dell Studio 1535 with Windows Vista and it will not turn on. When I press the power button the lights on it cycle on and off and I can hear the cd-drive like it is beginning to run. This goes for about 5 seconds and it all turns back off. I took it to the tech guy at work and he said it may be a motherboard issue. I would like to know if anyone has seen an issue like this or has an idea before I spend $200-$300 on a new motherboard. I only paid $500 for the laptop when I got it so if there is another fix for it that may be cheaper I would like to try that first.