You need Check Disk when there are errors on hard drives or external drives. Disk checking in Windows is able to repair file system errors (files messed up on the disk) and recover data from bad/unreadable clusters. If you haven't already done so, read Memory and hard disks article to find out basic information about hard disks and partitions.
Windows 8 and 8.1 are much more intelligent in detecting file system errors and they always repair them at startup (if you start or restart your computer). For hard drives, this means that in most cases no additional checks are required. You can still use Check Disk for detecting and fixing error on removable drives.
In case Windows 8 or 8.1 is checking a drive at startup, please let it finish - the check might take up to half an hour. Usually, it takes much less time, but rebooting while a drive check is in progress might mess files up even more, or result in an unbootable state.
Open (My) Computer from Desktop or Start menu or press Windows Logo+E on your keyboard.
To check the drive where Windows is installed, right-click on an item that ends with "(C:)", for example Local Disk (C:) or Windows (C:). In Windows Vista, 7, 8 and 8.1, the drive also has a small Windows logo (a four-color flag or a blue flag) on it. The drive might also end with "(D:)" or "(E:)" in case you have multiple operating systems installed. The drive or partition Windows is installed on is often called system drive.
All hard disks must contain at least one partition, but they may contain multiple partitions. Windows assigns each partition a different drive letter, such as C:, D:, E:, etc.
Drive letters A: and B: are usually reserved for floppy disk drives (FDD, often called "floppy").
You might have more than one hard disk or partition. In this case, repeat these steps for other items, too. You do not need to check CD/DVD or floppy drives.
Choose Properties from the menu.
Open Tools tab and click Check Now. In Windows 8 and 8.1, this is called just Check.
In Windows Vista, User Account Control will open. Click Continue.
In Windows XP, Vista and 7, Check Disk dialog opens, choose Automatically fix file system errors and then click Start button. If you want to perform an exhaustive disk check, also activate the Scan for and attempt recovery of bad sectors option. Please note that this test might take several hours to complete!
In Windows 8 and 8.1, usually a "You don't need to scan this drive" dialog appears. For system drive, click Scan drive to double-check; for other drives, click Scan and repair drive. If Windows 8 or 8.1 already knows there are problems with the disk, "Repair this drive" dialog appears instead. Click Repair drive.
If this is your second or third hard disk in Windows XP, Vista and 7, the disk check will usually be performed right away. Windows 8 and 8.1 will always run a check, even on system drive.
Windows XP always opens the "Disk Check Complete" message after the process is complete. Click OK.
Windows Vista, 7, 8 and 8.1 provide information on whether the scan found any errors. If the message says "Your device or disk was successfully scanned", there were no problems found and you can click Close.
In case the message is "Some problems were found and fixed" in Windows Vista and later, you can click the See details button or Show Details link to find out what exactly was repaired. In Windows 8 and 8.1, this opens Application log of Event Viewer, with event filter for Event ID 26226 applied.
Or just click Close if technical details are of no interest to you.
Do not forget to check other drives, too!
If this is your only hard disk or the one that has Windows XP, Vista or 7 installed on, you'll see a warning that the disk cannot be checked right now. This happens because many files are in use and cannot be checked while Windows is running.
In Windows XP, click Yes to schedule a disk check for the next restart.
In Windows Vista and 7, click Schedule disk check.
Restart your computer now to let the check run.
After restarting, a screen stating "A disk check has been scheduled" appears. There is also a countdown of 10 seconds and you can cancel the disk check by pressing any key on your keyboard within those 10 seconds.
But this is not what we want, right? Wait and see how Windows checks the hard disk.
It might take some time until the disk check completes. If you have a large hard drive full of data, the check might take even up to half an hour. In case you scheduled a complete disk check with testing for bad clusters, the test might run for several hours.
If everything is fine with the disk, Windows XP and Vista will start. Windows 7 will always restart your computer after a disk check.
In case Disk Check could not fix all file system problems with one run, the disk check will start over after the restart. Please let it finish (your computer might be restarted again) and wait for Windows to start - it is very important that your hard disk is working properly. Sometimes it takes up to three restarts to fix all errors.