is there any maor diference between DMOS and ACM
well if so which one is preffered and y?
is there an ACM available for oggvorbis...........where
can i get a working sample ACM to analyse the working of ACM

Google is your friend

There is an ACM version of vorbis, but I don't know exactly where.
There is also an ACM version of LAME in the LAME CVS/source code, under the ACM directory IIRC. IMO this should be a good starting point.

DMOs are supposed to be similar things but for DirectShow. So only apps that deal with DirectShow can use it. It was to make codec development easier without having to deal with the whole DirectShow shit...