How do I downgrade the OS on my BlackBerry?

1. Delete the newer OS from your PC by going to Control Panel >Add/Remove Programs.

2. Then download and install the older version of the OS. BlackBerry Operating System Downloads

3. Then locate and delete the file named "vendor.xml"

4. When that's done, simply plug in your device, open Desktop Manager and run Application Loader. The loader will downgrade the OS.