Can you open a Command Prompt(Admin) and enter chkdsk /f
You will be prompted to type y for it to perform after the next reboot.
Then enter shutdown /r /t 00 which will effect an immediate restart to allow it to continue.
The machine will restart after its completion where you should then open Event Viewer and when it has read the data, expand Windows Logs - click on Application/Action/Find and type chkdsk into the Find box and press enter.
Cancel the Find box to read the chkdsk report in the scrollable window below and check to see if it reports any KBs in bad sectors.
If it does, close off Event Viewer and open a Command Prompt(Admin) and enter chkdsk /r
This will transfer what data it can to safer parts of the HDD and then you should immediately create a system image onto something like an external HDD, although DVDs can be used.
You will also need to create a System Repair disk to boot up to restore a new HDD when that one eventually fails.
If the chkdsk report does not report any KBs in bad sectors then open a Command Prompt(Admin) and enter sfc /scannow and let me know what that reports and which version of Windows you are using.