Dell lists the driver for the card that was the latest one installed on those machines, but that is not necessarily the card that you have in yours.
What I did was, I typed the S. TAG number into the drivers page (www.dell.com/.../555) and check for the tab that has the SYSTEM CONFIGURATION, make sure you are looking at the ORIGINAL CONFIGURATION option and (CARD (CIRCUIT)..., WIRELESS..., MINI PCI CARD..., 1370, BROADCOM CORPORATION...) should be the card that was originally installed with the system from the factory.
Hope this can help.
Thanks!