Have you tried to restart the PC? Is the laptop booting the same way? Try to open the Advanced Boot Menu, pressing F8 on startup. Select Safe Mode and check if the laptop will boot. If not, use a Windows installation drive and boot from it. Select the Repair option and check if the problem will be solved.
Have you got the Windows repair disk? If you do, my suggestion is to try booting from the CD and then try to repair the system. You could do that by opening the Command prompt and entering the following command:
Wait for some minutes after that for the system to be repaired. Let me know what happened.