Hi John,
Thank you for posting your query on Microsoft Community.
I would require more information to help you better.
- Does the C Drive appear in Disk management?
- Have you made any changes to the computer prior to the issue?
- In which drive Windows Operating System is installed?
We need to check if there are any errors found for the hard drive that you are using.
a. Move the mouse pointer to bottom left of the screenwhere you see preview of start menu and right-click to bring up a list of Windows settings.
b. Click on ‘Command Prompt (Admin)’ to bring up elevated command prompt.
**Note:**Click ‘**Yes’**if it prompts for permission.
c. In the command prompt, type **‘chkdsk /r’**and press Enter.
Answer Ywhen ‘chkdsk’ asks you if you want to check the drive next time computer boots (restarts).
**Note:**While performing chkdsk on the hard drive if any bad sectors are found on the hard drive when chkdsk tries to repair that sector if any data available on that might be lost.
Also refer:
Optimize your hard drive
http://windows.microsoft.com/en-IN/windows-8/optimize-hard-drive
Keep us posted on the status of the issue we will be glad to help you further.