I recently encountered the following error on my Windows 7. I do not know what caused the error and searched the web. One of the solution was to register notification.dll. However, I was not able to find such a file.
There was also another option which was to reinstall Windows - from the Dell support (again listed on the web).
Finally, I decided to go through the services and disable "Broadcom Wireless LAN Tray Service". It seems to do the trick. I do not encounter the problem when I boot up my notebook. Hopefully it does not cause other problems.