What Is Check Disk Utility?

By Maxwell Payne

The Check Disk Utility, also known as CHKDSK, is a disk utility program found in Microsoft Windows. Use of this utility is part of the recommended routine maintenance for keeping a PC running at peak performance. The utility scans the hard drive(s) for bad storage blocks on the physical disk. Files stored on bad blocks may become corrupted or inaccessible, so the system attempts to identify and move those files before disabling those storage blocks.


Check Disk scans the physical hard drive(s) in a computer for physical errors and damage on the disk itself. In particular, the utility scans for bad storage blocks and alerts the user to the bad blocks and the files contained in them. If these blocks contain files, the system attempts to move these files before flagging the bad block and removing the block from regular use.


The basic mode of CHKDSK simply runs a complete scan and issues a report after the scan, identifying the bad blocks and the location of files on those bad blocks. With this mode, it is up to the user to identify affected files and move them from the bad blocks on the disk. The other two modes allow the user to adjust the settings of the utility. In the first of these modes, the utility can be set to scan and identify any bad blocks. Once these blocks are identified, the utility program tells the system to try to fix any file problems. The second mode is an in-depth scan of the hard disk and will scan the entire disk for bad blocks. When bad blocks are found, the utility tries to move any affected files to a new block on the disk before disabling the bad block.

Time Frame

As part of routine maintenance on a PC running Windows, Check Disk Utility should be run about once a month. You should not wait until there is an obvious performance problem; the utility should be run as a preventive measure to discover bad blocks before the data on them becomes corrupt. The actual amount of time it takes to run the utility can vary widely depending on a few factors. These factors include which mode is chosen, the size of the hard drive, the speed of the computer, and how much of the hard drive is already filled up. These things considered, it can take five or more hours to run a complete scan and repair or disable bad storage blocks.


Bad storage blocks on your hard drive can slow down the time it takes to access files, cause files stored on bad blocks to be inaccessible, or even cause your hard drive to freeze or crash. CHKDSK utility looks for these potentially damaging bad blocks and removes them from active use if they cannot be repaired. By removing bad blocks, the computer will no longer spend time trying to scan or access the bad blocks. Unfortunately, this can mean lost or corrupt files if the system cannot remove the files on a bad block before disabling access to that particular bad block.


While this utility can help detect and even tell the system to try to fix or disable bad blocks, it can only do so much. If a scan comes back showing a large number of bad blocks, either displayed as a number or a graph, it may be time to replace the hard drive itself. Replacing a hard drive with many bad blocks can be a preventive measure to keep your files and data safe. A drive with a large number of bad blocks could freeze or crash at any time, leaving your files trapped on an inaccessible drive.