that i beleive installs the drivers into your pc for your phone, so you can charge it via usb.. use desktop manager... use it as a modem....mass storage... etc.... etc....
Download Details
Software Name: BlackBerry USB and Modem Drivers ENG (DM4.5 B13)
File Name: BlackBerry USB and Modem Drivers ENG (DM4.5 B13).msi
Download Size: 12.335 MB
Published Date: 06/24/2008
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In some cases, you may require the functionality of the drivers but not the full BlackBerry Desktop Manager.
I have seen reports that the drivers need to be installed to enable battery charging from the USB port or see the phone as a USB storage device. However this is far from certain because my Bold 9000 just recognised and started charging when connected to a Linux (Ubuntu) netbook which had never seen a BlackBerry before.