SteamPowered User Forum
Start Battlefield 2 without changing anything.
Start the CD-Key Changer, type in your CD-Key and press Apply.
You have to run the tool as administrator!
If you don't want to use the CD-Key Changer, here the *.reg files:
Windows - 32Bit
Windows - 64Bit
Delete or rename this file:
C:/Program Files/Steam/steamapps/common/battlefield 2/installscript.vdf
Run Battlefield 2 as Administrator.
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: