MacBook Pro beeps and powers on after 5 tries

I have a MacBook Pro from mid 2009 annoying me.

When I turn it on, the led blinks rapidly, about 14 times, and then the Mac beeps once. The screen remains black and nothing happens. So I have to hold down the power button to force a shutdown. When I turn it on again, no beep or blinks, but still a black screen. I repeat that 3 more times and the Mac finally turns on and works normally. I use it, shut it down and when I want to use it again, I have to go through that process all over again: the beep, blinks and 4 tries until it comes back to life.

I've opened it and tried changing the memories, the hard drive, but no different results.

It's worth mentioning that I was reinstalling it for triple boot when that happened, however I've repartitioned the HD and it's back to the original state now, so I believe it does't have to do with that reinstall.

I'm not able to run the hardware test pressing D before startup, even with the original disc.

I googled for it but couldn't find any alike pattern.

Any ideas?