You installed succesfull Windows 7 x86 on a Dell Latitude D420 and wondering why you can’t install the Dell Wireless 5530 HSPA modem? If you get the following error from Windows 7 after installing the card in your notebook then you shouldn’t leave.
The first thing you should do, is downloading the correct Windows 7 x86 driver. At the time of my download, it it was R243926. The installer will abort with the error 23000 Authentication Error, like the following screenshot.
You should not close the error message, instead you should look for the msi installer in the temp folder of you profile. The folder looks like {5497CED3-F71E-44B1-9308-D9A15048540D}. There you will see Dell Wireless HSPA Mini-Card Drivers.msi. Now download the ORCA software from Microsoft, which can be used to edit msi packages.
After that you should open the msi package and edit the table CustomAction and delete (here is called Drop Row) the Action Authenticate. Please don’t forget to save the msi package and copy it from your temp folder. Now you can close your error message and run the copied msi package.
Everything should be fine now.
Be Happy. 
Microsoft Technique Unleashed 