I found another solution:
If you have Battlefield 2
Click Start.
Go to Run.
Type regedit and hit OK button.
Click on plus sign next to HKEY_LOCAL_MACHINE.
Click on plus sign next to SOFTWARE.
Double click on Electronic Arts folder.
Double click on EA Games folder.
Double click on Battlefield 2 folder.
Double click on ergc folder.
Data displayed will probably have x9392 only.
Right click on it and select Modify.
Type in x9392 and then your CD key.
note: don’t include hyphens.
Example: x9392(your Battlefield 2 CD key here)
AHHHHHH IVE TRIED THIS AND IT STILL WONT WORK!!!
Please can u help me, singleplayer is soooooo boring
Do i have to reinstall all of bf2???
Ive tried re-downloading and installing sandbox !!!!!!!!I DONT KNOW WHAT TO DO!!!!!!!!