A. You might encounter situations in which you want to ensure that a file is the same version and has the same content as another file (e.g., when you send a file to someone, you want to make sure it hasn't been corrupted or altered). A hash is an alphanumeric string that's generated according to a file's contents. If the file has been changed in any way, the hash value changes as well. Microsoft created a utility to generate hash values, which you can download at http://download.microsoft.com/download/c/f/4/cf454ae0-a4bb-4123-8333-a1b6737712f7/windows-kb841290-x86-enu.exe. The program, which extracts to a folder that you specify, consists of a readme file and the fciv.exe image, which generates the hash values. For example, to generate a hash for a single file, use this command:

fciv d:\temp\yodapepsi.mpg

After you enter the command, you'll see the following on-screen message, the generated hash value, and the corresponding filename:

//
// File Checksum Integrity Verifier version 2.05.
//
253f066ffa7c50e1e03fa588f23e3230 d:\temp\yodapepsi.mpg
To generate hashes for every file in a folder, simply specify the folder name, as this example shows:
fciv d:\temp
The command outputs information similar to this on screen:

//
// File Checksum Integrity Verifier version 2.05.
//
5d5d1f14c8704e935a87ad78fc535bea d:\temp\70298Training.pdf
8658bf85ba3ebe184c6d5cd0269a9e89 d:\temp\BO-DFRS Transcript.doc
427048a497768d91cd57e29fb0199d2b d:\temp\BODFRS Live Meeting.wmv
253f066ffa7c50e1e03fa588f23e3230 d:\temp\yodapepsi.mpg
The readme file contains more examples of how to use fciv.exe, including using different algorithms and generating hash values for entire tree folders.