The file you are looking for is in the windows system folder. It is ATRAC3.acm.
The sony file you downloaded is the install file and when you run it "installs" ATRAC3.acm and makes any adjustments to the register etc. It performs a complete install there is nothing else to do.
You can use audiograbber to encode a audio file into the ATRAC3 format. you have to go into audiograber and select the ATRAC format. After you install the codec you will have to reinstall audiograbber this allows audiograbber to "see" the ATRAC3.acm file and display the codec as an option. You can play the file back using media player, winamp or just about any third party media player that will play back wma and wav files. You will find the the ATRAC encoder creates a file with a .WAV extesnion yet it is 1/10 the size of the orginal wav file.
again thanks