WDM stands for Multi-Media Extensions. This is the model of audio drivers included in Windows 95 through XP, though Windows ME, 2000, and XP rely mostly on WDM drivers. MME is simply a method of getting audio from an audio application through Windows and to the audio interface. Unfortunately, due to its age, this is not a highly efficient method and quite often offers latencies of 100ms up to 750ms (3/4 of a second). Although sometimes latency can be tweaked down a bit and be nearly usable for pro-audio, this method is rarely used today when realtime processing is required.