Does your laptop respond to any Function keys? Try tapping F8 when you power on, and see if you can get into Safe Mode. Also try F11 to see if you are offered Restore. Otherwise you will need to create a Windows 7 Installation disk or a Windows 7 Repair disk. If that is not possible apply to HP for Recovery disks. There is also a possibility that your HDD is failing.
If u r faced the problem before then u simply said hdd problem edit that. if the problem arived f8 and f11 not show any option.reason the bootmgr is the first file know about how to start windows.