This often comed up from a bad hard drive, try to reseat the drive, and boot off a utility disk that has drive tester software. Ultimate Boot CD has several. Run a drive test. If it comes up good, try usng the TestDisk utility to fix the boot sector. If that fails, you should get a new drive for the laptop, install Windows on that, and use yours in an external enclosure to copy the files from if it's readable.