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:
Start the CD-Key Changer, type in your CD-Key and press Apply.
You have to run the tool as administrator!Step 3:
Delete or rename this file:
C:\Program Files\Steam\steamapps\common\battlefield 2\installscript.vdfStep 4:
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 5:
Try out if it works. If you still get the error, go back to Step 2 and tick the "Don't include hyphens" checkbox before pressing Apply.
If it works:
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