Also, if the suggestions above do not work. Download and run the utilities from your HDD manufacturer (such as Seagate's Sea Tools). If you want a good fill defragmenter, try Power Defragmenter. It is a GUI for contig from Sysinternals. Download Power Defragmenter 3.0
Download and extract to a folder. Click on the Power Defragmeter exe. It will prompt you that contig was not found, and download it for you. Or you can download contig from the Sysinternals site 1st. Contig
Just make sure both files are in the same directory. It also has a triple pass mode which is what I used when my OS was on a HDD.