Boot up function corrupted...I think.

Hello-

I have a Dell desktop with Windows XP for my operating system. My computer has crashed. By that, I mean that I am unable to reboot the computer. I keep getting the black and white screen that says there was an error with the start-up and gives me options to reboot (ie. safe mode, last settings that worked, etc). I have tried every options and it just continues to fail to boot and brings me back to this screen.

I have a friend who repair computers who is out of town, but he felt that this was fixable and sent me to this forum to get some assistance until he returns.

Anyway advice would be very much appreciated.

DocHari