I can't tell you exactly how to do it, because it depends on what platform you are using. Basically you need to find a program that can convert your Apple Lossless files back to WAV (XLD, among others, can do this on a Mac). Then re-rip the same cd to WAV. It would be best if you did this on the same computer with the same drive and program as you used originally, as it is possible to introduce minor differences with different hardware or a different configuration. Then figure out how to generate an MD5 sum on a file or group of files on your platform, and compare the results.
