Share 'Black screen says, "Unbootable device... press any key to continue"'

Hi I'm new here and with the mac. So, last time i tried to install windows Xp in my mac book. It succeed. I removed the windows Xp partition yesterday through the bootcamp in the mac partition. Later, when i restart the mac book.. "the black screen" appears after the white screen with the "welcome" sound.. and it says Unbootable something and it stops there. The funny thing is, I still can acc…