Blinking yellow light on Dimension 3000

Hi, I had to move out to another country and finally after 2 months I plugged my pc back, but it doesn't start. The fans on both processor and power supply work and a green light on the mother board is on, but the power light blinks yellow and the hard drive light is solid green. The hard drive dont start and nothing appears on the monitor. I read some of dell documentation (http://docs.us.dell.com/support/edocs/systems/ws340/en/ug/codes.htm#1161590) and it says there is a system board failure. I tryed contacting Dell support but it seens my service tag and registered name doenst match, so the only way I can solve this is by myself :/
Does anyone knows what could it be or how to fix it?