I installed Monkey's Audio version 3.97 and then 3.99 (the newest one), but 3.97 doesn't work properly anymore then. It tells me MACDII.dll (or so it's called) version is wrong. Are 2 different working Monkey versions, idependent from each other, not possible ?
Why do I want to have this ?
Well, maybe I don't want to change a working Monkey, since a lot of archieved music depends on it.
Or when uploading to HA, I want to offer an older version so people with no new versions can also decode/listen to the samples. It's not possible to decode *.apes encoded with version 3.99 using version 3.97, and it doesn't depend on the compression mode (I tested this.)

I've succesfully decoded hundreds of .ape files encoded with Monkeys versions that are up to 3 or more years old, using 3.99 without one single problem. I don't think you have anything to fear unless you've used strange tagging techniques.

Yes, but you cannot decode 3.99 bitstreams with an 3.97 decoder and that is what he said if I got him right. So, to preserve compatibility with users still having the 3.97 decoder, he would have to encode APE files using the 3.97 encoder.