Deleting the vendor.xml is necessary when the OS being installed was not released by the carrier branded on your BB (i.e. Installing AT&T OS on a TMo BB.) If you don't delete the vendor.xml when necessary the OS won't load at all. Since your 8100 is AT&T branded you didn't *need* to delete the vendor.xml. I just always include it in the instructions because inevitably it becomes an issue if I don't.
The only reason I can think of why memopad, tasks and brickbreaker are missing is that they may have been unchecked in the Application Loader. Simply plug in the BB and run Application Loader again and make sure the boxes are checked. If they are not, then simply check them and finish out the installation again and they will be added.