I just want to add to this. me7sum is a command line program. If you just double click the executable you'll get a quick flash, then it'll close. Some people aren't as adept with CMD as others, so I copied this from another post I had made.
Download the file (me7sum), put it in your user directory (C:\Documents and Settings\usernamehere) along with the bin (we're going to call it IN for this example).
Hit START, RUN, and type: CMD
Then, type:
me7sum IN.bin OUT.bin (keep the names short for simplicity's sake)
You'll see the program running in cmd, and will end up with a new file with the checksums corrected in the same directory you placed the previously mentioned files (C:\Documents and Settings\usernamehere). The corrected file will be named OUT.bin (or whatever you select when typing the command)
NOTE:
usernamehere is to be substituted with whatever your actual user name is. It may be administrator, it may be steve. For me, it's user1. You can run the file from wherever you place it, but having the program and bin in your user directory allows for a very simple cmd line.