as i see lot of people have problems updating their bbs to new OS
either they brick their device or while updating they get FATAL ERROR
FOLLOW THESE STEPS TO UPDATE UR BBS WITHOUT ANY TROUBLE OR RISK OF BRICKING
1) go to blackberry site and download os of ur choice
2) go to c:/program files / common files/ reseacrh in motion/ app loader /
and delete vendor.xml file
3) install the os
4) again go to same path as step 2 and delete vendor.xml file
5) dont use desktop manager
6) make sure ur OS is in following folder
c:/program files / common files/ research in motion/ shared / loader files
7) go to app loader folder and double click on loader.exe
8) it will open up apploader wizard click next , it will show list of available updates
9) type next and select options as per ur wish
10) it will take 10-20 mins and ur device will be updated safely