Knowledgebase
How to perform an MD5 hash check in Windows
MD5 hash checks are performed to verify that a file you've downloaded on your local computer is exactly the same as the original file on the server from which you've downloaded it. This is done to make sure that the file was not hacked during the download.
As an example we'll use PuTTY, an application for accessing hosting accounts through SSH for Windows users. The official site of PuTTY's developer has the MD5 checksums for the files it offers for downloading. You can find links for these checksums, as well as the files themselves, on the download page.
For example, if you want to download the PuTTY installer package (putty-0.61-installer.exe), you have to compare the MD5 checksum of the original file (it's provided on the site) with the MD5 checksum of the file you downloaded on your local computer. If there are both the same, everything is fine.
To find out the MD5 checksum of the file on your local computer, you need a suitable tool that works on Windows. One such tool is File Checksum Integrity Verifier (FCIV). You can download it from the support section of Microsoft's site.
After you download it, install it on your local computer. Then run the command prompt (Start>Run>type cmd>OK). Then you have to add FCIV to the system path. To do it, type the following command in the command prompt: set path=%path%;c:\fciv. Of course, that's provided that FCIV is installed in a folder called fciv on your local C: drive. If the path is different, just change the last part of the command.
After you type the command press Enter on your keyboard. To see the MD5 checksum of the file, type the following command in the command prompt and press Enter: fciv.exe c:\putty-0.61-installer.exe (don't forget the file type, e.g. .exe). Again, the path to the file is just an example. After you execute the command you should see the file's MD5 checksum, and you can compare it with that of the original.
For some more information and screenshots check out the tutorial on performing MD5 checks.