When computers save files on their hard drives, they do so using record-keeping systems called 'file systems'. Occasionally running a program to go through that file system and verify the records there is one of basic tasks of computer maintenance. Follow the steps below to use the built-in file system checker in Microsoft Windows: (you may need to be an administrator on your machine to do this)

1.  Click on 'Start', and begin typing 'This Computer'.  Then click on the list entry for 'This PC'.

2.  Right-click on your 'C:' drive, and select 'Properties' from the menu.

3.  In the 'Properties' window, select the 'Tools' tab, and click on 'Check . . .' in the 'Error Checking' box.

4.  Since Windows does periodic checks on it's own, it will ask you to approve doing one manually.  Click 'Scan drive' to continue.  Windows will automatically attempt to repair any errors, and report it's actions in with a pop-up.