08-13-2008 02:45 PM
Check the following link: BlackBerryOS 4.x Download FAQ
Find your wireless operator in the list, go to the operator's site, download software (if it is present for your device model), and install it.
08-14-2008 02:05 AM
Check this link
There is a description how I did update handheld OS to 4.5 downloaded from another carrier.