Turn off pin 13 on startup? Arduino Mega

I'm working with the Mega 2650, and need all the PWM signals for a lighting fixture for an aquarium. I'm also using a touch screen lcd display for the GUI which apparently limits my PWM signals even further. In all, I need to use pin 13 which is activated and fired several times when the arduino starts up. Is there a way to program the arduino so it won't do that? Thanks

I don't think so... that happens before the user sketch kicks in, as far as I know.

I find it most annoying, must say, so I often include code at the top of my sketch to switch it off: of course that might be too late for you if the pin was already "talking" to your external system by then.

It is a function of the boot loader, so you need to hack into that and reflash it. You will need a programmer to do this. You can use another arduino as a programmer.