Sorry for bumping an old thread but I have a DW5550 card from an old Latitude that I've installed into my new E7440 machine running Win 8.1
The drivers/installer on the DELL site won't run, complaingin that this card isn't supported on this machine, but using the drivers in the first post I was able to get the card installed through Device Manager (thanks for that )
The problem after that is the DELL Mobile Broadband Manager then says that "the mobile broadband device is not found" despite showing correctly in Device Manager.
To solve this, I followed the instructions posted here:
https://www.bios-mods.com/forum/Thread-Need-help-with-E6410?pid=68254#pid68254
... and then reinstalled the DELL drivers which passed the authorization check this time. Now working perfectly