If CCleaner is not already running, open Start Menu by clicking on Start button or pressing Windows Key on keyboard.
Window XP users should choose All Programs, find CCleaner folder and click CCleaner:
Windows Vista and 7 users should type "ccleaner" into Search box and click CCleaner in search results.
In Windows 8/8.1 Start screen, type "ccleaner" (you do not need to open Search charm) and click it in the results. Touch-screen owners can just scroll to the end of Start screen and tap CCleaner.
As CCleaner needs administrative rights for cleaning temporary files and registry, User Account Control will pop up. Click Continue (Vista) or Yes (7 and 8).
Since version 3.19, you can disable User Account Control prompts in Advanced Options of CCleaner. Open Options tab on the left and click Advanced. Then enable the Skip User Account Control warning option.
As some of you might already know, just deleting files and emptying Recycle Bin will not really delete the files from hard disks, floppies or removable disks. This will just add a special bit to the file to specify that the file is not needed anymore. The files will actually remain on the disk until it gets overwritten. If you have a large hard drive with plenty of free space, this might happen only in several months or even a year.
Normally, you wouldn't care much about this knowledge, but what if you want to sell your hard drive or removable drive? Even if you format the disk, the files are still just marked as unneeded and they are recoverable. Worse still, you will not normally format your computer's hard disk if you need to sell your PC with Windows on it.
That's where CCleaner can help you. Its Drive Wiper allows secure erasing of free space or whole disks so that files cannot be recovered.
Just click Tools on the left and open Drive Wiper tab. From the Drives list, select the drive or drives you need to wipe. In this example, the "Elements (H:)" drive is a removable USB hard disk.
Select either Free Space Only or Entire Drive (All data will be erased) from Wipe combo box:
Next, select a wiping method from Security.
- Simple Overwrite (1 pass) is the fastest, but most insecure method. This will overwrite free space or whole disk just once, very comparable to formatting a drive.
Use this one only if you do not have any sensitive data on the disk.
- Advanced Overwrite (3 passes) refers to the DOD 5220.22-M method in NISP Operating Manual, a U.S. standard for handling classified information. This one has pretty good security and you should use it if you do have some sensitive data on the disk and you have no plans selling the disk to strangers.
- Complex Overwrite (7 passes) is basically an enhanced version of the previous method. Overwriting data 7 times is certainly safer than 3 times, so use it if you have sensitive data on the disk. But overwriting 7 times takes more than twice the time, too.
- Very Complex Overwrite (35 passes) refers to Peter Gutmann's method of securely erasing data. 35 passes is the most secure method available, as it uses completely random data during overwriting processes. This method takes very long time to complete and you should use it only if you have extremely sensitive data on the disk and you are about to sell the disk to some complete stranger. If you are about to throw the really important disk away, just destroy it with a large hammer and then burn it twice using gasoline - this takes much less time and makes the data really unrecoverable.
After making your selections, click Wipe.
The wiping process might take from a few minutes to several days, depending on the size of the disk (or free space) and the selected method for secure erasing.
The example below uses Simple Overwrite (1 pass) on hard disk, so it does not take long time.
By the way, Windows 8 and 8.1 have brand new Reset your PC feature that can be used for securely wiping personal data and resetting Windows to its defaults before refurbishing, selling or recycling your device.