Check the md5 sum of any file (How to?)
For windows you need to download the md5sum binary. I recommend the one from my dev-host.
After that, copy the file you're trying to verify to the directory where where you downloaded the "md5sum.exe"
Once that is finished, do SHIFT+RIGHT CLICK (inside the folder window) and choose "Open command window here"
Then type the following ("fileNameHere" must include the extension):
That will output a hash, which you can compare to the ones above.
Linux: No need to download anything, md5sum binaries are included in all distros, as far as I know.
Open a terminal and type the following ("fileNameHere" must include the extension):
$ cd path/to/download/folder
$ md5sum fileNameHere