If you started encountering an Invalid CDKey error message .....

For Battlefield 2142 DVD edition follow the steps below:

Double click on the My Computericon.
Double click on drive C:.
Next double click on Programs Files.
Double click on Electronic Arts.
Double click on Battlefield 2142.
Double click to open Support.
Double click on the Battlefield 2142_code.exefile.
Input your Battlefield 2142 Registration Code.
Note: If you are not prompted to enter your code, skip to step 11.
Click on next.
Close My Computer.
Click on the Start button.
Click on Run.
Type regedit in the text field.
Warning: Changes to the registry can cause your computer to operate improperly, so please follow these instructions exactly as they are written.

Follow these steps to back-up the registry so that should something go wrong, you can restore your system back to a working state:
Click the Start button.
Click on Run.
Type regedit into the available text field, and press OK.
If you are using Windows 2000/XP, click on File, and select Export. Note: If you are using Windows 95/98/ME, click on Registry
Then select Export Registry.
Select All under Export Range.
Type backup into the File name field, and click Save.
Click the plus sign next to HKEY_LOCAL_MACHINE.
Click the plus sign next to Software.
Click the plus sign next to Electronic Arts.
Click the plus sign next to EA Games.
Click the plus sign next to Battlefield 2142.
Click on the ergc. On the right panel screen, double click on default.
You should see a code under Value Data.
Enter x9392 at left most part of the code. (eg. x9392DH34DF78WE35BV78AS69)
Click OK.
You may now start playing the game online.

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For the EA Link version follow the steps below:
Double click on the My Computericon.
Double click on drive C:.
Next double click on Programs Files.
Double click on Electronic Arts.
Double click on Battlefield 2142.
Double click to open Support.
Double click on the Battlefield 2142_code.exefile.
Input your Battlefield 2142 Registration Code.
Note: If you are not prompted to enter your code, skip to step 11.
Click on next.
Close My Computer.
Click on the Start button.
Click on Run.
Type regedit in the text field.
Warning: Changes to the registry can cause your computer to operate improperly, so please follow these instructions exactly as they are written.

Follow these steps to back-up the registry so that should something go wrong, you can restore your system back to a working state:
Click the Start button.
Click on Run.
Type regedit into the available text field, and press OK.
If you are using Windows 2000/XP, click on File, and select Export. Note: If you are using Windows 95/98/ME, lick on Registry
Then select Export Registry.
Select All under Export Range.
Type backup into the File name field, and click Save.
Click the plus sign next to HKEY_LOCAL_MACHINE.
Click the plus sign next to Software.
Click the plus sign next to Electronic Arts.
Click the plus sign next to EA Games.
Click the plus sign next to Battlefield 2142.
Click on the ergc. On the right panel screen, double click on default.
You should see a code under Value Data.
Enter x9392 at left most part of the code. (eg. x9392DH34DF78WE35BV78AS69)
Click OK
You may now start playing the game online.