Hello, in this post i will show you how to fix the invalid cd key error, this will only work if you have a valid cd key. To fix the error do the following
1) go to start then run and type in regedit, this will open up the registry editor. 2) expand the hkey_local_machine, then expand software, then look for electronic art, then battlefield 2 and then ergc 3) now you should see a long number beginning with x9392 delete everything in that value except for x9392 and enter in your valid cd key, capitalize all letters also do not put spaces or hi-fin in between it should be one long thing like x9392123456789123456789
this way can also fix the invalid cd key error in battlefield 2 special forces just go to battlefield 2 special forces folder instead of battlefield 2 folder.