Laptop starts without power button

I have an HP Pavilion dv2000 and it turns on whenever I plug it in, and doesn't boot up. The power button won't turn it off and nothing happens except for the fans running, and lights turning on. This laptop has been sent in for repairs in the past and came back without a certain problem fixed and I believe that they did an improper flash on the bios or some RAM just isn't seated right. I can't get to the RAM, and the bios can only be flashed from within windows. Any help would be greatly appreciated.
Thank you,
Nyrol

"The power button won't turn it off" I take it that you are holding down the power button to force it of. I'm not an expert but I think it is a hardware problem (motherboard) as forcing the pc off via holding down the power button would be directly related to the hardware and not the bios etc. Not sure...

When I plug the battery in, it doesn't turn on, but the second I plug the power cord in, it turns on. I haven't seen anything like this before, but the laptop is out of warranty so I don't think there is any point in getting this repaired.

Sounds like a hardware problem and not a software problem... sorry