Can't find my Mac os after installing windows on bootcamp

PLEASE HELP!
This is my first post so I hope I am doing this correctly. I installed windows xp on my MacBook using bootcamp. It brought up an error message " press any key to restart" but pressing any key wouldn't work, so I held down the button to turn it off. I have tried every way possible to boot it up and get on my computer, nothing works! When I hold the option key while starting the computer, I only get a picture of a lock and under it a place for a password, never seen this before, my password doesn't open it. I put in the leopard cd and restarted it holding the c key and nothing, it brought up the same error message "press any key". Could I have wiped out the Mac os completely? I'm at a loss, any one have any ideas that I could try?

Your post was moved to this forum. "Running Windows.........."

It sounds like you may have overwritten your Mac partition when you attempted to install Windows XP. Try this:

Reset the PRAM. Try rebooting again to see if you can get into OS X. Also try booting again with your Leopard DVD.