This can be a bad hard drive. Boot to the BIOS, see if there is a hardware check utility there, scan the drive and see what the result is. You can also run a drive test using a boot disk like HIRENS or Ultimate Boot CD, they both have disk check programs you can run.
If it's a bad drive, replace it and install Windows again. If your other drive is usable at all, you can get an external USB drive bay and copy your files over.