|Are you shutting the computer down the proper way? |
Download SIW.exe to determine the brand of your hard drive. Then download the drive fitness utility for your brand and model drive.
Hard drives come with spare space on the drive. As surfaces get defective they are replaced with new. The fact that your drive is reporting bad sectors indicates that all the spare space has already been allocated and now you are losing capacity. That may be an indication of a failing drive.
If you don't already maintain backups of your personal files, as you should, I suggest you make them before the drive goes out on you.