How to Calculate Checksums in Windows

The checksum allows you to verify that a file you downloaded wasn't tempered with.

A checksum is a string of character calculated using complex a mathematical formula so one string of character is unique to one file. Checksum is used to be sure a file wasn't modified between the moment the creator made that file available and you receiving it. The two dominant checksum are MD5 and SHA1.

Instructions

1. Download FCIV from the Microsoft website. Save the file on your desktop and double-click on it when downloaded.

2. Click "Yes", browse to "C:\windows\system32\" and press "OK" to extract the file.

3. Go to the "Start" menu, click on "Run," type "cmd" and press "Enter" if you are using Windows XP. If you are using Windows Vista or 7, go to the "Start" menu, type "cmd" in the "search for programs and files" field and press "Enter."

4. Type "fciv name-of-the-file" in the "command Prompt" window to calculate the MD5 checksum. Type "fciv --sha1 name-of-the-file" to calculate the SHA1 checksum or "fciv --both name-of-the-file" to calculate both.

Tips & Warnings

• The command prompt window default to opening at the root of your profile. If the file in on your desktop type "cd desktop" before the "fciv" command.

• If you wish to install the checksum software in another folder than the "c:\windows\system32," type "set path=%path%;c:\where-you-installed-fciv."

References

• Microsoft: Availability and description of the File Checksum Integrity Verifier utility

Resources

• Microsoft: fciv command and options