make sure you have all your data you want on your blackberry (address book, options, etc)

now uninstall everything that has to do with blackberry and research in motion from your computer, including the .ipd backups of your blackberry.

then go into the registry (regedit) and delete the research in motion registry files under HKEY_CURRENT_USER > Software. then delete the research in motion folder.

restart your computer

install desktop manager 4.6 first

then install the new os you want to put onto your phone. (at time of posting the best one seems to be .217)

start dm

now plug in you blackberry to your pc.

it should read it and ask to update

viola. good luck