If a missing Broadcom driver prevents you from launching your
computer, you can proceed as follows:

1. Type or copy the following command into the terminal:

2. Add the following line at the end of blacklist.conf document:

Save the document and close it.

3. Remove needless Broadcom drivers by the following two terminal commands:

4. Restart the computer

5. Install the appropriate drivers for the 12.04 system by typing

6. Remove this line at the end of sudo gedit /etc/modprobe.d/blacklist.conf

Save the document and close it

7. Restart the computer

8. Open the following settings by typing

9. Add the following short line at the end of the document:

Save the document and close it.

Let us know if these steps were useful.