I'm guessing the obvious is happening here; bad hard drive. Usually if you hear ticking or some sort of noise from HD you can suspect bad hard drive. Do as suggested above and Backup your files immediately also look into replacing hard drive. After backup see if you can create a restore disc from your system. If you can't, try and create an image as soon as possible. Then run a chkdsk /r in the command prompt. If you were able to create a restore disc. Good luck.
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