If you want to know how to run computer diagnostics, you can begin with Scandisk. This diagnostic program is included in Windows. This utility will scan the computer's hard disk, check for errors and correct problems it finds, if possible.
To run computer diagnostics on Windows XP, click the Start button and open My Computer. To run computer diagnostics on Windows Vista or Windows 7 (on which this PC diagnostic tool is called Check Disk), click Start and open Computer. Right click the disk you want to scan, which will likely be "Local Disk (C:)," and select Properties from the right-click menu. Go to the Tools tab of the Properties dialog box and click the Check Now button under Error Checking. Select the check boxes for Automatically Fix File Errors and Scan for and Attempt Recovery of Bad Sectors. Click the Start button.

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If you selected to run a diagnostic scan on your primary computer drive, which is usually C, the utility will schedule a scan the next time you start your computer. For your convenience, set up Scandisk just before you turn off the computer at the end of the day. Then, rather than just shutting it down, restart the computer so Scandisk can run its diagnostic scan, which can take quite a bit of time.