Install the latest 4.2 Desktop Manager from here (4.2 SP2 is even newer and includes the new Roxio Media Manager and can be downloaded from this same site):
BlackBerry - BlackBerry - Sys Req V4-2 Pack 1
Then install the .64 OS.
Then you can replace the Blackberry.alx file with the edited one from Jibi's thread here:
http://www.blackberryforums.com/ring...-4-2-only.html
Plug in BB, Open Deskotp manager and run Application Loader. You should see "update" next to "core applications." Finish the installation.