Why are you doing this so complicated? There is a much more easier way:
-Install Desktop Manager version 126.96.36.199
-Install version 188.8.131.52
-Close Desktop Manager
-After installation go to C:\Program Files\Common Files\Research In Motion\AppLoader and delete vendor.xml
-Start Desktop Manager
-Connect your 6710 or 6720 with 16MB to your PC and click "Next"
-Follow the instructions on the pc screen and update your device