Do you have the Windows recovery discs? They probably came with your laptop or you made them before installing anything new (when your laptop's windows was still pristine). Use the recovery discs to take your windows to the point it was in when you first bought it. THat should help clear out any booting problems. Otherwise, see below...
If that doesn't work then try the following,
You have to go to bios and do a factory reset. BIOS reset is the only way.