The first thing I would do is grab a Linux Live Distro..... something like this one
http://www.linuxmint.com/edition.php?id=159 Pick a mirror site close to your location and create either a Live DVD or Live USB thumb drive from the iso and boot from that and promptly attempt to determine if you can rescue your critical data to an external resource (USB hard drive).
After that I would then obtain
http://www.acronis.com/en-us/personal/pc-backup/ There's a free trial link on that page which I believe will work for 30 days or so.
You should be able to create the rescue media on another computer and use that to boot the problem machine and create an image of the system, using the advanced options to tell it to ignore bad sectors.
Then I would probably remove the drive from the problem system and attach it to another computer using one of any number of USB docks or cable connection to accomplish this and then you can determine if the drive is still functioning within a Windows environment to further rescue any critical data and or perform further diagnostics (another check disk, defrag, scan for malicious software, etc.,).
Lastly replace the drive in the problem machine and boot from the installation media and try using some of the advanced trouble shooting utilities under the repair options and see if you can get things back up and running again.
You didn't say what the results of the chkdsk you performed actually were. Right above where it said "completed" there should have been some information regarding what was actually performed on the drive and if there was any data in "bad sectors".
If the drive is having mechanical problems, clicking noises or vibration issues or even bytes in bad sectors is may be on its' way to failing and require a replacement.