With this guide you can fix the Invalid CD-Key Message for the Battlefield 2 Complete Edition.
This should work for Battlefield 2 and Battlefield 2 Special Forces.Step 1:
Download the Battlefield 2 CD-Key changer.Step 2:
If you know which Operating System (32-Bit or 64-Bit) you have go to Step 3.
If you don't know which OS-Type you have, go to
Start->Control Panel->System and Security->System
There you can check if you have a 32-Bit or 64-Bit OS.Step 3:
Start the CD-Key Changer, choose your Operating System, type in your CD-Key and press Apply.
If you get an error, please run this tool as administrator!Step 4:
Delete or rename this file:
C:\Program Files\Steam\steamapps\common\battlefield 2\installscript.vdfStep 5:
Run Battlefield 2 as administrator.
Right click on "C:\Program Files\Steam\steamapps\common\battlefield 2\bf2.exe"
Properties->Compatibility->Check "Run this program as an administrator"->Apply->OKStep 6:
Please report if it works or if you have any problems.
Also check out this thread:http://forums.steampowered.com/forums/showthread.php?t=1680864