Hdd
Your hard drive is on the razors edge of failing, or has already failed. I hope you had your files on backup. I'd recommend buying an external hard drive, backup the files you have to have, then install a new hard drive to your computer and copy transfer your backup files files over if possible. That is if the info on the old failing HDD is not replaceable.
And/Or you could take the chance (and time) needed to run a diagnostic utility on the hard drive (most manufacturers have one). But, you don't say much about the computer, like brand, model, modifications, any recent problems, when it was purchased, what kind of shape it's in (good/bad), have there been any any changes from stock configuration, any major changes to the OS software or the computers hardware.
Does it take a long time to bootup, run programs, save anything, etc...? Are there any unusual sounds (e.g. clicking) and/or smells (like something burning), coming from the computer?
If you are getting SMART notifications, then I would bet cash that the HDD is VERY near death, or is already dead. Those warnings are usually like seeing the grim reaper (he's coming for your hard drive). Sorry to say it!