Boot Camp goes to Black screen with start-up modes but only restarts to same screen

I have an older MacBook and when I bought it, from a friend, it already had windows running on it. Just the other day I went to restart my computer and all I got want the black screen saying that the computer was turned off wrong and to choose the start up mode. I tried the last known option and nothing happened besides restarting to the same screen. Then I tried the normal mode and that didn't work and safe mode did the same thing, starting back up to the black screen. Is there something that I can do/fix, or does this require some professional help? Thanks!

XP, I think.

I have been asking computer guys at work but they refuse to even look at it because it is a mac.

When I hold the option key I have the choice of getting to the mac or pc part of the computer and I can get back to the mac side without problems. I just can't get past the black screen when I need to get to the pc side.

Is there a way to get rid of the pc side and then re-add it with a windows software disc maybe?