The message you are getting means that your hard drive is no longer bootable. Its hard to say what the reason is because there is no one definite cause. Your hard drive itself may have physically gone bad or you may have some corrupted system files. You an try going into the BIOS to make sure that the drive is still recognized by the computer.
If you aren't getting any specific error messages as to what files are corrupt or missing if any then you may be stuck doing a reinstall of Windows. If you have your recovery CD that came with the laptop then you can use that to reinstall your system. You might have a recovery partition on the same hard drive instead so it might not be accessible in your case. Keep in mind that the recovery CDs that come with laptops usually wipe out the computer and put it back to the state it was in when you bought it meaning any programs or files you added since then will be gone.
Before getting that drastic you can have someone take the hard drive out of your laptop and attach it to a working computer and see if its recognizable and if so copy your documents off of it before reinstalling Windows.