Can I install the BB OS or only my carries OS (Vodafone)

Hello everybody,
I'm new with blackberry�s, I have a unlocked Vodafone 8820 with 4.2 OS and want to know if I can use the official BB OS software or do I need to download my carriers OS (Vodafone).
When I connect to the BB desktop software I get the option to install the BB 4.5. Can I install the software without problems? Or can I only install my carries OS?
If I start the wizard and go to the last step, I get a warning that the device must be activated before being able to make phone calls or receive email. Can I activate my BB after installing the BB OS without problems? Is that possible?
I need to be sure before going ahead with the installation; I don�t want to make my BB unusable.
Thnx in advanced!

Installing an OS is not difficult, but it is not trivial either. If you are new to BlackBerry devices, some of the steps in the procedure may be confusing. The Upgrade Procedure that's linked in my sig is a good guide. If you use your BlackBerry for a while and get familiar with it, the process will be easier.

You can install any carrier's OS that matches your phone. That means it has to be an 8820 OS. You cannot use an 8800 or 8830 OS. Typically the OS that DM tries to install will be your carrier's OS. You can activate your phone after installing an OS. It IS possible to make your phone unusable if something goes wrong in the OS upgrade process. Those problems are usually correctable.

JeffH,
Thanks for the info. Now I can upgrade my BB. Once again thanks a lot for all your time!