Desktop Manager - Program for your desktop. Version 4.2 is available for download, and includes Device Switcher and Media Management (for handhelds with 4.2 or higher).
Handheld OS - Operating System for your Blackberry. Currently the 8100 is the only handheld that offers version 4.2. 4.1 is the current highest for BBs such as the 8700 series.
OS 4.2 is NOT available yet for anything other than the 8100 series. Believe me when I say that it will be all over this forum when it is. I promise.