Computer keeps restarting over and over again

Hello,
Every time that I power on my computer, a black screen comes up with text. It says "We apologize for the inconvenience, but Windows did not start successfully. A recent hardware or software change may have caused this."

After this, there is a list of choices: Safe Mode, Safe Mode with Networking, Safe Mode with Command Prompt, Last Known Good Configuration and Start Windows Normally. Now, if I hit enter on any of the Safe Modes, a bunch of code at the bottom of the screen appears. Then, my computer restarts. If I hit enter on either of the other two, the Windows XP loading logo thing appears, then it restarts again. So, I basically can't get into my computer. HELP!